1. Did you do the speaker set up in the Denon receiver? You need to do that so the receiver knows what speakers you have, how far from you each one is, and what level to play them You will hear pink noise from each speaker so you know they are active. The sub level is set by ear with music and movies. The other channels are set to be the level at your seating position.
2. If you are playing a stereo source select a surround mode for stereo music, movie, or game in some cases.
3. If you are playing a 5.1 source set the receiver in auto mode for most sources. For stb or ova tuner set the receiver to Dolby. If you set the surround mode for those to auto most receivers will either do Dolby Digital or stereo rather than Dolby Digital or...