Start with easy stuff first. Go into the TV menu's and look through the audio sections. You want Digital, not PCM. Maybe you have to enable the SPDIF out. Then, note the label on the digital in for the Denon. There are 4 coax SPDIF in's on that model if memory serves, each marked something different (TV, DVD, etc I would assume). Make sure the Denon is set to output the signal on whatever label you have that cable going into.

Does the Denon work with outher sources?