Allow pop ups in your browser
DO NOT CHECK DONT USE FB API UNLESS YOU GET A MESSAGE FROM THE ADDON
If your a chrome user, you need to accept the security pop up when you open a MW tab .
(1) Give all permissions, going to main configuration and click "All permissions".
or use this link:
If that doesn't resolve the issue:
(2) Can you see your Mafia Wars feeds from THIS LINK?
YES: Reload the game and make sure you're connected with Facebook.
(3) NO: Have you blocked Mafia Wars Posts?
Go to your news feeds page, on the highlighted menu at your left side (News Feeds button), if you over the mouse, will appear a pencil.
Click it and click on Edit configuration. Here you'll see all your hidden apps. Remove Mafia Wars.
Did it resolve the issue?
(4) NO: You've a known facebook issue.
Go to HERE and Report as follow: