We just purchased a battery Nest doorbell. My partner was able to add it to both his iPhone and iPad. I cannot. When I “add device” it prepares, connects and then I get a message saying there was a problem, I have tried to do this at least 30 times, have checked my settings, made sure I hadbeen added as a member of the Home. Called the Help line and got a call back immediately but there was so much static on line that I could not hear the help desk person.
You would not add it to your phone as a new device. Instead your partner, who originally set it up, would add your account to the home that the device is in. Add Device is the process to set it up and configure it to work, connect it to wi-fi, etc. That process adds it to a "Home" in Google Home. In Google Home App -> Settings -> Household your partner should add you as a member of the household. Any mobile device that you are logged into that has Google Home will be able to view and control the doorbell.