Thanks @benbusse, it seems composer update fixed the problem, though I'm not sure yet what the issue was.
The detailed error I was getting from the server was: "An active access token must be used to query information about the current user"
Here's the full log trace:
{"error":{"context":null,"message":"Client error: `GET https://graph.facebook.com/v2.6/me?access_token=&fields=name,email,gender,verified&appsecret_proof=3d5e939901971b9f62a0e0015a8d1ca532dd670f0b4c2e3d1f00ffaf2c7c48c1` resulted in a `400 Bad Request` response:\n{"error":{"message":"An active access token must be used to query information about the current user.","type":"OAuthExce (truncated...)\n","code":400,"trace":["0 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/guzzle/src/Middleware.php(65): GuzzleHttp\\Exception\\RequestException::create(Object(GuzzleHttp\\Psr7\\Request), Object(GuzzleHttp\\Psr7\\Response))","1 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/Promise.php(203): GuzzleHttp\\Middleware::GuzzleHttp\\{closure}(Object(GuzzleHttp\\Psr7\\Response))","2 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/Promise.php(156): GuzzleHttp\\Promise\\Promise::callHandler(1, Object(GuzzleHttp\\Psr7\\Response), Array)","3 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/TaskQueue.php(61): GuzzleHttp\\Promise\\Promise::GuzzleHttp\\Promise\\{closure}()","4 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/Promise.php(246): GuzzleHttp\\Promise\\TaskQueue->run(true)","5 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/Promise.php(223): GuzzleHttp\\Promise\\Promise->invokeWaitFn()","6 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/Promise.php(266): GuzzleHttp\\Promise\\Promise->waitIfPending()","7 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/Promise.php(225): GuzzleHttp\\Promise\\Promise->invokeWaitList()","8 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/promises/src/Promise.php(62): GuzzleHttp\\Promise\\Promise->waitIfPending()","9 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/guzzle/src/Client.php(129): GuzzleHttp\\Promise\\Promise->wait()","10 /opt/bitnami/apps/dreamfactory/htdocs/vendor/guzzlehttp/guzzle/src/Client.php(87): GuzzleHttp\\Client->request('get', 'https://graph.f...', Array)","11 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/socialite/src/Two/FacebookProvider.php(103): GuzzleHttp\\Client->__call('get', Array)","12 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/socialite/src/Two/FacebookProvider.php(103): GuzzleHttp\\Client->get('https://graph.f...', Array)","13 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/socialite/src/Two/AbstractProvider.php(207): Laravel\\Socialite\\Two\\FacebookProvider->getUserByToken(NULL)","14 /opt/bitnami/apps/dreamfactory/htdocs/vendor/dreamfactory/df-oauth/src/Services/BaseOAuthService.php(91): Laravel\\Socialite\\Two\\AbstractProvider->user()","15 /opt/bitnami/apps/dreamfactory/htdocs/vendor/dreamfactory/df-core/src/Resources/UserSessionResource.php(85): DreamFactory\\Core\\OAuth\\Services\\BaseOAuthService->handleOAuthCallback()","16 [internal function]: DreamFactory\\Core\\Resources\\UserSessionResource->handlePOST()","17 /opt/bitnami/apps/dreamfactory/htdocs/vendor/dreamfactory/df-core/src/Components/RestHandler.php(268): call_user_func(Array)","18 /opt/bitnami/apps/dreamfactory/htdocs/vendor/dreamfactory/df-core/src/Components/RestHandler.php(174): DreamFactory\\Core\\Components\\RestHandler->processRequest()","19 /opt/bitnami/apps/dreamfactory/htdocs/vendor/dreamfactory/df-core/src/Components/RestHandler.php(221): DreamFactory\\Core\\Components\\RestHandler->handleRequest(Object(DreamFactory\\Core\\Utility\\ServiceRequest), '')","20 /opt/bitnami/apps/dreamfactory/htdocs/vendor/dreamfactory/df-core/src/Components/RestHandler.php(169): DreamFactory\\Core\\Components\\RestHandler->handleResource(Array)","21 /opt/bitnami/apps/dreamfactory/htdocs/vendor/dreamfactory/df-core/src/Services/BaseRestService.php(75): DreamFactory\\Core\\Components\\RestHandler->handleRequest(Object(DreamFactory\\Core\\Utility\\ServiceRequest), 'session')","22 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(17089): DreamFactory\\Core\\Services\\BaseRestService->handleRequest(Object(DreamFactory\\Core\\Utility\\ServiceRequest), 'session')","23 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(17061): DreamFactory\\Http\\Controllers\\RestController->handleService('v2', 'user', 'session')","24 [internal function]: DreamFactory\\Http\\Controllers\\RestController->handlePOST('v2', 'user', 'session')","25 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9132): call_user_func_array(Array, Array)","26 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9194): Illuminate\\Routing\\Controller->callAction('handlePOST', Array)","27 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9174): Illuminate\\Routing\\ControllerDispatcher->call(Object(DreamFactory\\Http\\Controllers\\RestController), Object(Illuminate\\Routing\\Route), 'handlePOST')","28 [internal function]: Illuminate\\Routing\\ControllerDispatcher->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","29 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(52): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","30 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(17266): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","31 [internal function]: DreamFactory\\Http\\Middleware\\AccessCheck->handle(Object(Illuminate\\Http\\Request), Object(Closure))","32 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","33 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","34 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","35 [internal function]: Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","36 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9651): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","37 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9175): Illuminate\\Pipeline\\Pipeline->then(Object(Closure))","38 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9162): Illuminate\\Routing\\ControllerDispatcher->callWithinStack(Object(DreamFactory\\Http\\Controllers\\RestController), Object(Illuminate\\Routing\\Route), Object(Illuminate\\Http\\Request), 'handlePOST')","39 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(8230): Illuminate\\Routing\\ControllerDispatcher->dispatch(Object(Illuminate\\Routing\\Route), Object(Illuminate\\Http\\Request), 'DreamFactory\\\\Ht...', 'handlePOST')","40 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(8217): Illuminate\\Routing\\Route->runController(Object(Illuminate\\Http\\Request))","41 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(7931): Illuminate\\Routing\\Route->run(Object(Illuminate\\Http\\Request))","42 [internal function]: Illuminate\\Routing\\Router->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","43 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(52): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","44 [internal function]: Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","45 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9651): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","46 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(7932): Illuminate\\Pipeline\\Pipeline->then(Object(Closure))","47 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(7923): Illuminate\\Routing\\Router->runRouteWithinStack(Object(Illuminate\\Routing\\Route), Object(Illuminate\\Http\\Request))","48 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(7913): Illuminate\\Routing\\Router->dispatchToRoute(Object(Illuminate\\Http\\Request))","49 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(2419): Illuminate\\Routing\\Router->dispatch(Object(Illuminate\\Http\\Request))","50 [internal function]: Illuminate\\Foundation\\Http\\Kernel->Illuminate\\Foundation\\Http\\{closure}(Object(Illuminate\\Http\\Request))","51 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(52): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","52 /opt/bitnami/apps/dreamfactory/htdocs/app/Http/Middleware/AuthCheck.php(183): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","53 [internal function]: DreamFactory\\Http\\Middleware\\AuthCheck->handle(Object(Illuminate\\Http\\Request), Object(Closure))","54 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","55 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","56 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","57 /opt/bitnami/apps/dreamfactory/htdocs/vendor/barryvdh/laravel-cors/src/HandleCors.php(42): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","58 [internal function]: Barryvdh\\Cors\\HandleCors->handle(Object(Illuminate\\Http\\Request), Object(Closure))","59 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","60 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","61 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","62 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(17368): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","63 [internal function]: DreamFactory\\Http\\Middleware\\FirstUserCheck->handle(Object(Illuminate\\Http\\Request), Object(Closure))","64 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","65 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","66 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","67 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(13113): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","68 [internal function]: Illuminate\\View\\Middleware\\ShareErrorsFromSession->handle(Object(Illuminate\\Http\\Request), Object(Closure))","69 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","70 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","71 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","72 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(11656): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","73 [internal function]: Illuminate\\Session\\Middleware\\StartSession->handle(Object(Illuminate\\Http\\Request), Object(Closure))","74 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","75 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","76 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","77 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(12852): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","78 [internal function]: Illuminate\\Cookie\\Middleware\\AddQueuedCookiesToResponse->handle(Object(Illuminate\\Http\\Request), Object(Closure))","79 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","80 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","81 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","82 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(12789): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","83 [internal function]: Illuminate\\Cookie\\Middleware\\EncryptCookies->handle(Object(Illuminate\\Http\\Request), Object(Closure))","84 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","85 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","86 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","87 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(3286): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","88 [internal function]: Illuminate\\Foundation\\Http\\Middleware\\CheckForMaintenanceMode->handle(Object(Illuminate\\Http\\Request), Object(Closure))","89 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9666): call_user_func_array(Array, Array)","90 [internal function]: Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illuminate\\Http\\Request))","91 /opt/bitnami/apps/dreamfactory/htdocs/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(32): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","92 [internal function]: Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))","93 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(9651): call_user_func(Object(Closure), Object(Illuminate\\Http\\Request))","94 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(2366): Illuminate\\Pipeline\\Pipeline->then(Object(Closure))","95 /opt/bitnami/apps/dreamfactory/htdocs/bootstrap/cache/compiled.php(2350): Illuminate\\Foundation\\Http\\Kernel->sendRequestThroughRouter(Object(Illuminate\\Http\\Request))","96 /opt/bitnami/apps/dreamfactory/htdocs/public/index.php(53): Illuminate\\Foundation\\Http\\Kernel->handle(Object(Illuminate\\Http\\Request))","97 {main}"]}}