Hi James, and welcome to the forum!
I'm assuming that you mean that you get no sound from the TV speakers when you play some source (blu-ray player, cable box, etc.) that is connected to the Denon. Is that correct? If so, check out page 144 of the Denon manual. You can either listen to audio from the speakers attached to the Denon, or through the TV...but not both unless you connect your source to both the Denon and the TV.
EDIT: If you have the Denon set up to pass through HDMI signals to the TV when the Denon is in standby, it will pass the audio to the TV in that case.