If you're unable to visit any of your friends in-game, please first try restarting your device. If that doesn't solve your issue, 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 in the bottom right of Ollie Land, are you seeing your Facebook friends?
- Did you try logging out and logging back into your account through Free > Account?
Once you send this info our way, we should have a much better idea of how to solve your issue. Thanks!