Whomever is controlling the Facebook URL Redirect needs to add forums.pineboxentertainment.com to the Facebook app whitelisting.
If you change the URL to “community.gomorragazette.com” the Facebook sign-in works.
Edit: Facebook error in question “Warning
URL Blocked: This redirect failed because the redirect URI is not whitelisted in the app’s Client OAuth Settings. Make sure Client and Web OAuth Login are on and add all your app domains as Valid OAuth Redirect URIs.”