Thank you.
Right now the STB is connected to TV by HDMI. Sound is ported out tfrom TV o audio receiver by optical cable. Audio receiver not integrated other than receiving digital sound via optical cable.
I initially had the STB connected to TV by HDMI and ported sound directly out of STB to audio receiver by optical cable. Was able to control volue level this way, but still no 5.1 Dolby.
What seems to be telling is that the 5.1 icon does not appear for any channel in the VZ channel guide with the Moto STB. When I stream via the LG Fios app, many HD channels display the 5.1 icon (in additon to the "CC", rating, "SAP" and other icons) in the VZ channel guide. When viewing those channels, 5.1 is triggered on my audio receiver. If I switch over to STB and tune same channel - no 5.1 sound and no icons in the VZ channel guide.
The receiver does not support HDMI, so all input is by optical cable, dig coax, or dig din (plus analog). I have a new receiver on the way, but I don't think the problem is the receiver because 5.1 works when it gets the signal. Unfortunately I'm beginning to think the STB doesn't do 5.1 ... or VZ has disabled it. I'll reroute connections make sure I covered all the bases with STB audio direct to audio receiver.