This article assumes you to know how to gain access to the Unifi Controller and are familiar with the interface. The current controller software as of 2/3/2017 is 5.4.9 and is set to automatically upgrade firmware in Settings > Site > Automatically upgrade firmware. If automatic upgrading isn't working and manually clicking Upgrade Firmware in the controller interface also isn't working do the following:

HFS Screenshot:    Once installed:

  • Click Menu
  • Add Files
  • Choose the new firmware
  • Copy the path in the bar at the top (which will be an HTTP path with your IP:port/filename.bin)
  • Click the AP you want to upgrade in the Unifi controller
  • Click Configuration
  • Click Manage Device
  • In the "Custom Upgrade" section paste the path
  • Click Custom Upgrade and confirm

The upgrade will take several minutes to complete and will disconnect all connected devices. Upgrading more than 4-5 at once will cause the upgrades to fail. If you wait at least 30 seconds between each firmware upgrade you can upgrade 5 APs with no problems. I did 10 on my second run rapidly and all failed. I assume this is either a limitation of the HTTP server or the controller that's brokering the upgrade.

Upgrade firmware without a controller: