...
Check the LC of the game and make sure there is a LCI installed on the controller that matches.
If the asset number of the game changed during an upgrade / theme-change make sure you delete the old asset out of quickconfig and reboot the game.
If the issue is with only one game, you may need to:
Delete the asset from quickconfig.
Reboot the game.
Re-add the game to the progressive pools.
If the issue is with all the games:
Check the network and switch for power and connectivity
Log into the controller and make sure services are still running.
...