Did you test it on a HDMI TV to make sure it is even putting out audio over HDMI? I know that the Skyrocket (android phone) doesn't all the time only if it "feels" like it (Im sure it has to do with the item its connected to). I know also that there is, in settings, a check mark for "audio out when docked" (something like that) maybe check that? I would start by connecting it to a TV with HDMI just to make sure it is even outputting audio. Hope this helps a little.