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".
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:
[O] I don't see activity from other people, pages or applications in my News Feed.
Description: Here you must say that you can't see news feeds from games, like Mafia Wars.
ScreenShot: You should take a screen of your browser when loading THIS PAGE.
No .. The supported browsers are Firefox and all firefox clones ie.. Comodo dragon Palemoon Chromium browsers and clones ie .. cool novo icedragon rockmelt (rockmelt is not advised)..
There are 2 so called trippel engine browsers that can use the addon but it needs a little hack.