Optical output on Stream box work?

I have wireless headphones that connect to a transmitter that uses an optical audio input.

This setup has been working when connected to the TV, but this requires changing the TV's audio out setting to PCM each time I want to use the optical output (But if I just leave it set to PCM, then then the ARC signal going back to the receiver is only 2.0 and not surround)...so now that I have the Stream box, I've moved the optical connection over from the TV to the box. I can see light at the end of the cable that plugs into the Stream box...but I never get any audio from the headphones.

I've been through the configuration options on the Stream box and I'm not seeing anything that I can change that might help.

Is there something I need to do to make this work? Is the optical output on the box actually supported?