I'm not with PTSP but a couple of things to check;
Have you changed your phone recently? I had and it took a while to realise that the app / online service had a "primary device" setting. So even though I had switched my SIM, the notifications were being sent to my old phone.
With my app (BOI), if the push notification doesn't appear, I can open the app and on the login screen there is an option to check for notifications i.e. don't need to login to the app. I think it's in case push notifications are blocked or don't show.
In your phone settings you can check the app permissions to check that the app has full access for notifications