Unable to change ownership of a Ring Video Doorbell Pro

Our office had a video doorbell pro installed by an interior designer who had since gone bust and unreachable. While trying to reset the doorbell, it tells us that the device is registered to a different owner and we can't seem to get this information from the application which seems to have removed all previous settings after an OS upgrade. Anyway, a month ago, I called the number (1800 8700 9781) who said that the MAC address and serial number does not exist in the database and he can't help me. It's quite strange since if it is not a legit device, we shouldn't be able to use the app to register at all. Also, there is also no way to send a picture of the device with the serial number or QR code. In the month since, we tried our best to contact the designer but cannot reach him. We really need some support and wonder what we can do next. Please advise.