HereLink Air Unit telemetry port not working

we have an Air Unit with a telemetry port that suddenly stopped working.
No connection to vehicle possible.
Pairing and video works though.
Eric at HEX forwarded me to this forum.

Any help appreciated.

First thing I would do if it was working and nothing has changed on the FC side check the cable with a Multimeter or if you have a compatible one try another.

Second make sure you turn off Location on the Herelink ground station as there is a known bug that affects telem.

What FC are you using and can you confirm the settings

Cables good, Location off.
PixHawk Cube black with latest ArduCopter 3.6.11
Multiple boards tested.
Another Air Unit works fine.
Hardware problem?

Have you tried to reload firmware into the air unit?

Yes already tried unfortunately.