I’m having the same problem with my pro.
Installed all was working correctly for a day then I deleted it by accident from the ring app. So I’ve tried the holding Side button for 30 seconds but it boots up flashes white for a second then the top half of the button flashes blue.
I’ve removed cover on the left side to access the USB port. And I’m currently charging it as I’ve read it could be battery. But still no difference. All I want is for it to go back to factory and have the circling white light to set up.