Sometimes when you upgrade firmware of access points (AP) through the UniFi controller interface, AP hung in Upgrading state (eg UniFi AP PRO).
When you restart AP, it does not change state and AP does not reach.
In this case, you need to upgrade AP firmware via command line.
It is assumed the server is installed on Linux
- Determine controller version and firmware code:
Version: execute command on the server
ls -l /usr/lib/unifi/dl/firmware/BZ2/
resulting directory is version number
Firmware code determined by the table: