Gemini Air Dolby surround support?

I just got a Gemini Air device and a new Direct TV account a few days ago. The settings are driving me nuts, specifically the audio output. I am connecting it through a Sony home theater receiver, and although the only audio setting I see is set to "surround", the receiver does not detect a Dolby signal via the HDMI connection. Many other devices I've used send Dolby Digital to my receiver, but no matter what I do I can't get this one to work.

The setup info on the website is terrible. Even when I log in, the "troubleshooting" page shows my equipment but the info is all wrong. Am I an (Edited per community guidelines) or what?

Thanks

Tom in NC