CONNECT TO ONLINE MODES FOR ANDROID
1. Check that you are updated to latest version of the app.
2. Check that you are logged into Google Play Games and have the latest version of the Google Play Games app installed.
3. Go to About > Help > Sign in to Play Games on the app.
If you still cannot sign in, try the following:
Check that your Multiplayer Notifications are enabled.
Check that your Google Play Games settings are correct.
If you are still unable to connect to online modes, try Google Play Games Troubleshooting.