Only iOS devices stop receiving notifications after a few days of the app being installed. To resolve this, you need to reinstall the app again. I'm using Firebase to send messages.
Push notifications are not being delivered by FCM
You would want to contact Firebase for this. There has been no attempts to send any notifications to your app since March 28th.
The last notification that was sent was delivered successfully. So, there are no notifications, because none are being sent.