Can't set up doorbell because it is owned by previous owner of the house

I have contacted the previous owner who says he has transferred ownership to me but when I try to install it, I can't because it is still registered to the previous owner. I called the help desk and they said they would help me if I can give them the MAC address. They say it is on the back of the unit, but the screws have been stripped and I can not remove the device. Is there any other way to transfer ownership? Beyond frustrated.