Receiving STUN errors on Unifi controller running on cloud hosted server like Digital Ocean or AWS. You have already allowed the STUN port 3478/UDP and still receive a STUN error like this:
“This device is not able to connect to the internal STUN server. Please check if the device is able to reach the STUN server on port 3478.”
If you are using an elastic ip with AWS or a floating ip with Digital Ocean this may be your problem. The STUN request goes to the elastic ip/floating IP, but the server responds from it’s own ip address instead of the floating/elastic IP. This causes the STUN error in the Unifi controller.
Dont’ use a floating/elastic IPs with hosted Unifi controller.