Check the firewall on the unit hosting the controller. Port 8080 should be open for communication between the device and controller. Quick test is to drop the firewall and if that’s the problem, it will immediately start talking to the devices. Once they are found and brought up to date, enable the firewall. Communication will continue if port 8080 is open. I’ve had this happen twice on an Ubuntu box when I physically changed the switch port it was connected to and obtained a new IP address on the same subnet. This was with port 8080 open.
After another incident and watching the devices panel, it turns out that all devices need to be adopted again when the IP address of the controller changes. For device adoption port 10001/UDP needs to be open. Just tested this and it worked without having to drop the firewall.
Jerry's blog 
Just wanted to say thanks, I found this a little over a year after you posted it. I just migrated my Unifi Controller over to a test lab Windows Server 2019 box after upgrading to the latest version (using 64 bit OS) on my Raspberry Pi and finding that after a few minutes of running the controller the Raspberry Pi 4 locked up solid and the controller obviously stopped working. As soon as I allowed access to these ports in Windows Firewall the devices connected to the controller immediately.
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Just wanted to say thanks, I found this a little over a year after you posted it. I just migrated my Unifi Controller over to a test lab Windows Server 2019 box after upgrading to the latest version (using 64 bit OS) on my Raspberry Pi and finding that after a few minutes of running the controller the Raspberry Pi 4 locked up solid and the controller obviously stopped working. As soon as I allowed access to these ports in Windows Firewall the devices connected to the controller immediately.
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