something very strange happens to me and I wanted to know if someone has happened to him. I have the Notifications configured through Azure Notifications Hub, everything goes fine on the day, notifications arrive. The next day, they do not arrive anymore, what I have to do is uninstall the App and delete the data, install it again and the notifications begin to arrive without problems until the next day. It's very weird and I do not find that it could be failing. 
From the Azure control panel, when I sent a test notification. For that device I get the error
The Push Notification System handle for the registration is no longer valid