I just had this happen after a power outage. In my case, the controller is on a surge protector, so I think mine was just affected by the outage alone.
See the link below, but here is what I did.
1 - Pulled the power and re-powered quickly to get the beeping to stop. In my case that took several tries.
2 - The controller did not connect to the hub, so I tried to remove it via the app.
3 - The app wouldn’t remove it so I tried to Force Remove it. ST would not Force Remove reporting that the device was “working properly”.
4 - The device still had not connected to the hub. However, when I checked a bit later, it was connected and working fine.
5 - I haven’t pulled the power to see what would happen during the next power failure.
I’m thinking after you get the beeping to stop just let it sit for a while to see if it reconnects.