Thanks for posting here in the Community. To know more about this issue, I'd like to ask if you're referring to your Nest Doorbell? Was ADT installed your doorbell? What app are you using to see that your Camera is unreachable?
Just checking in to make sure that you've seen our responses. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.