Some background information
The app is programmed such that, once your game data is backed up to your Google account, we require that it always be connected to Google Play Games Service--the app would be vulnerable to certain exploits if we did not require this. The way we enforce the requirement is by setting a flag in your game data saying "this person has a cloud save" and checking for that flag before allowing you to play.
Why am I getting this error?
Your game data has the flag (see previous paragraph) set, but the app doesn't think it's currently connected to Google Play Games Service.
What should I do in order to play again?
Click the Sign In button and sign in to Google Play Games Service. The sign-in button can be found in the Options menu.
What if I don't want to connect to Google Play Games Service?
The game won't require the connection to Google Play Games Service if your save data has never had the flag set. So, if you are willing to start over from the very beginning, you can play without being connected to Google Play Games Service. To do so:
- Reinstall the game, start over from the very beginning, and never do anything with Google Play Games Service (not even loading the cloud save). You will unfortunately have to re-earn the progress you've made up until now. A second downside is that the app won't backup your game data to your Google account.