Problem Link to heading
A device is shown offline even though it was adopted in the past. This has happened to me when I changed the IP of the UniFi Network Controller.
Solution Link to heading
SSH into the USG device and run the following command
set-inform http://192.168.50.11:8080/inform
Adoption failed, and the device is still disconnected Link to heading
You should try to UniFi - Reset Device, and then re-adopt the device from the UI.