Ring Doorbell Has Disappeared?

Hi, I wonder if anyone could help me.I've had a Ring Doorbell for about a year and noticed that it didn't appear to be connecting to my phone any more.I've just logged onto the app and the device has completely disappeared. If I try to add the device again it comes up with a message saying it is still registered to its owner. The bell is still connected to the chime demonstrating that it is still connected to the Wi-Fi.At first, I was concerned that maybe I have been hacked. However, I haven't needed to charge the battery for a long time and when it was working normally I had to charge the battery often. Also, my app is only linked to my phone. Does anybody know if this is a common problem or if there is a quick fix for it?