AudioFuse Studio - not working Audio Out over USB

I’ve had my Audiofuse Studio for over two years and this issue just popped up randomly. I’m able to use the audio interface to record audio in to my Mac Mini (and my MBP), but when the AFS is selected as the system Audio Out destination, absolutely nothing gets played back or comes through. I normally listen to all of my system audio using headphones plugged into the AFS headphone jacks, but nothing now… the jacks seem to work fine as I’m able to monitor guitar, synthesizer and microphones plugged into the AFS no problem.

I’ve tried resetting the AFS and installing latest firmware, swapping to a different USB-C cable to connect to my Macs, testing on two different Macs, and even taking a look at the “Audio MIDI Setup” app on my Macs as some previous posts seem to recommend. Everything looks fine…

Is there something obvious I’m missing? Does it make sense physically for the AFS to somehow be able to send audio over USB-C but not receive it?

Any help or suggestions appreciated!