KenC -
Well, let's see -
Version of 3CX to include Service Pack level would be a start. The pperating system in use and whether 32 or 64 bits would also help. You titled the thread as STUN Resolution Failure and the lastest SP reportedly fixed a bug with STUN (on 64 bit systems, but perhaps in not in your case as it was reported as a fix involving STUN and one-way audio). Given the title of the thread and the error code with no explanation of where observed, any ill -effects, any logs, or if any conditions existed at the time of the observation....we are all guessing.
How often does the error occur, is this new or has it been going on for a while?
Do you have a fixed public IP at the location where 3CX is located? Do you need STUN?
It may also simply be that the STUN server was down at the time. I know that 3CX has had some issues as of late keeping the servers alive, but they may have been able to resolve by now. If you don't need STUN, then turn it off and use your fixed IP instead.
