If you are like me you have you some UniFi devices on a different subnet than your UniFi controller. Trying to provision an access point that doesn’t automatically discover is still possible using the Ubiquiti Discovery Tool but there is another and much easier option.
To make this happen all you need to do is enable L2 network discovery option in your UniFi controller. Log into your UniFi controller and go to the Controller Settings section. Depending on if you are using the classic (old) or new UI this will be in a slightly different spot.
In the classic (old) UI you will find this right in the middle of the screen for Controller Settings Section.
In the new UI you will find this in Controller Settings, then go to the Advanced Configuration section.
Once enabled and saved, you can return to your device discovery section and give it a few minutes for your devices in different subnets to appear. That’s it!