Hi TPUC,
I don't own a Flex Panel - so sorry for some guessing.
What kind of Headset/Phones do you use?
Have you tried different Phones?
Do you use a 3.5-6.3mm adaptor?
Is any of the used/converted Jacks a TRRS instead of a TRS Jack?
What is the impedance of your Phones?
Is your TriCaster Mixer setup: is the Phones Out mixer switched/linked to the Flex Out output?
Can you use the audio inputs inside the TriCaster?
What TC model do you have?
Something you can try for now, is changing the Receive Mode in the Flex Web UI. Changing this setting to anything different, seems to kick the audio output active.
There is a new update file for the Flex CS panel available for download. It's the same version number, but this new one is a 'full' install versus an 'update' install and will be accepted on the Flex CS.