First, you could try to find your friends in "Play With Friends", a blue button on the main page.

If you can't find them, try to find "Create a new account" or "Return to guest mode" to log out with your Facebook. Then click "Switch accounts" to log in with Facebook.

If these solutions can't help with this problem, try to uninstall and reinstall the game to refresh your friend's list.

We made an update on Friend List because it was mentioned by players many times that when they remove Facebook friends, the in-game friend list will be synchronized with Facebook friends, meaning your friends will disappear from your in-game friend list when they are unfriended on Facebook