Vudu/Oppo audio problem

I will admit that I am not much of a home theater guy so I have little knowledge of some of the intricacies involved. On occasion we will rent a movie using Vudu which I source through my Oppo 103D. the audio output goes direct to my Dac. When I play Vudu movies I get no audio and have to use the poor quality speakers on my Panasonic TC-P50GT50 Plasma TV. When I play Youtube or some other source the audio is just fine. I have changed some settings on the TV to no avail. Is this a format compatibility issue between the movie audio file from Vudu and the Oppo? I would appreciate any help. FYI, this is not a component connection issue and I have the latest firmware downloaded to the Oppo. Looking for ideas, thanks!