@darrr1 First I need detailed information.
Do you use only this game and sms? No WhatsApp (or any other App which should receive Push Notifications)?
Does the problem only occur with the game?
If yes, you must go to settings / apps /name-of-the-game to storage - delete there data and cache.
(Before you do this may you use a inbuilt Backup Function inside the App, cause you loose with this step the data)
Delete the App. Reinstall it from Playstore, Login (if the App uses Login)
Go back to settings and check the steps in Post #2
Or do you have any other Apps which didn't receive Push-notifications?
I must say, I use same Rom and all my Push-notifications working as they should, during day and night. No problem at all, even not with sleeping mode - with the right settings from #2 ...
Apps which are restored from a Backup has Problems with Push-notifications!
Those Apps must be new installed.