No sub output when streaming music?

[GA_RR]

I've got an older Xbox 360 that I use as much for streaming audio from my computer as I do for gaming. I hook it to my receiver via fiber and have never had any issues for the last couple years playing music from it.

However, I just noticed yesterday that when streaming music I had no sub output. Troubleshooting my entire home theater system I've narrowed it down to only happening from streaming music, or anything playing on the Xbox not in 5.1. Has anyone run into this before? Has there been a recent update that came down that might have done this or are there any setting on the Xbox or computer that might have been changed to cause this?

TIA