If you have Facebook friends who play C.A.T.S. and they have connected their Facebook accounts to the game as well, but you cannot see them, please do the following:

1. Open Facebook application and navigate to Settings & Privacy > Settings > Apps & Websites >  C.A.T.S. > Remove App > Remove

2. Reinstall the game itself (do not forget to check that Cloud synchronization is turned ON in the game options, otherwise you will lose your progress).

3. Launch C.A.T.S. and complete the tutorial. 

4. Go to Options and log in to Facebook. 

5. Open Facebook app and go to Settings & Privacy > Settings > Apps & Websites >  C.A.T.S.  and make sure that "Friend List" is enabled.

6. Enjoy the game!
If that doesn't help, your friends may have unfriended you on Facebook or disconnected their accounts from the game. That's always sad, so we hope that's not the case.