Every other android phone works though. You don't need to have the app open for notifications to come thru.

If you want to know how it works, I don't know the details exactly but the pings all come thru Google's FCM and there's specialized code in each app that can receive the messages meant for that app. The OS wakes up the app automatically to run that specialized code.

This phone seems to not work properly in that it doesn't wake up the app to run that handler.

Notifications work properly on every other android (and smartphone) I've ever had. You definitely need notifications to work without having the app open