Problem statement
When trying to login using the Facebook social connection the login fails, and the following error is generated:
Error Accessing App
We’re sorry, but the application you’re trying to use doesn’t exist or
has been disabled.
Cause
The application you created in the Facebook Developer portal is disabled for some reason. Sometimes Facebook does this for compliance or other reasons.
Solution
Login to the Facebook Developer portal and re-enable the app that was created for the Facebook social connection.