In my experience, processing notification does not appear all the time, you might try more times.
Android has this concept in place to run long running tasks and not to kill them by the OS (as was the frequent case in Minibits before). Might be they are sometimes not long enough?
There should always be the confirmation notification about completed payment.
I am not so worried about not seeing the notification. Sometimes even could be annoying if you are in the middle of something.
I want more to be sure that the zaps are received with the app closed, just working in background.
Background processing is currently used only for paying over nwc, not receiving.
There is separate push notification sent from lnurl server when receiving to a lightning address. However that's only notification and wallet claims ecash only when app starts. Reason is that wallet can't rely that push notifications are allowed and working and still receive.
