User clicks a button and allows push notifications. In the phone’s settings the app shows up with notifications “on.” In the app, a field is checked that indicates user allowed push notifications.
When user stops allowing push notifications from the phone’s settings, how do I get a message back to the app to uncheck the “allow push” field?
I don’t think you can. There is a reason why browsers don’t allow persistent requests like this. It would be annoying to the user. The user already answered the request for notifications. They will never be asked again.
At that point, their only option would be to go into their browser settings and clear any site settings or specifically change the setting to allow notifications for that site again.