Hi @Ljf! Anytime a Ring device is attempting a setup on another Ring account, and it has not been released from the prior Ring account, a change of ownership process will apply. Removing it in the Ring app is a great first step. Upon attempting a new setup, an email will be sent to the previously setup Ring account email address to request authorization to change ownership.
Check out our Change of Ownership process for more information on this process. I hope this helps! 