Facebook: Fix this error- “App not setup the developers of this app have not set up this app properly for Facebook Login”

• How to solve this error: “App not setup: the developers of this app have not set up this app properly for Facebook Login”

1. Go to https://developers.facebook.com
2. Login into your app
3. Left-panel> “App Review“. In “Make <app-name> public?” -> choose Yes
4. Left-panel>”Settings“. “Contact Email” -> enter the email being used in the tested device (not sure this step is mandatory)