You can only see your Facebook friends in-game if you have signed in with your Facebook account and your friends have done the same. Please keep in mind that you cannot visit any Facebook friends who have not already installed the game.

If you're still unable to visit any of your friend in-game, please try restarting your device. If that doesn't resolve your issue, then please follow up with answers to the following questions:

-Are all of your friends missing or just some?
-When you click on the invite button on the bottom right of Ollieland, are you seeing your Facebook friends?
-Did you try logging into a different account and back into your original through Settings > Account Info?
-Have you changed your password recently?

Once you send this info our way, we should have a much better idea of how to solve your issue. Thanks!