This problem is most likely connected to your Facebook privacysettings. Please open your Facebook Homepage and go with the mouse on the Ratsapp on the left side. Click the cogwheel and select "Edit settings". At the top you will seethe option "App visibility". Please select "Friends" in the drop downmenu. Now you should see your Facebook friends who are already playing thegame in the friends window of the app. With the "invite" button youcan invite more Facebook friends to the game.