It’s a known issue with Samsung phones not reserved for just Gems of War. @Kafka educated me about it. The only way to avoid it is to keep your phone out of sleep mode or “unlocked” 24/7. Otherwise sometimes the notification will be right on time. Other times it won’t go off until you go to unlock your phone (making a 1-30 minute delay)
Completely separate issue.
Salty asked for more information. The community in large ignored the request so nothing is being done. And Salty ignored my last request to find out exactly what devices (if any) the rewards notifications it’s actually working on.
(Again. That’s twice today. )
I don’t see such an option on Android 11.
Can you show a SS? All I see is battery optimization junk and run in the background which I have .
(Again. That’s twice today. 
)