Can we confirm that the issue you are experiencing is in the testing version of ZK1 (1.11.1)?
Could you describe what you see when you access the Rankings page, for example. Are you able to tap the 'Add' button, and see your friends list?
Do also try to reconnect your game to Facebook:
- Exit the game app
- Go to your Facebook page in a web browser on a computer, or use the Facebook app
- Look for your Account Settings, click on Apps on the left hand menu and find the Zen Koi 1 app
- Remove Zen Koi 1 from the list
- Return to your game, and re-connect it to Facebook