A:Answer I actually purchased this receiver as a gift but (based on your question), your DVD player may only provide audio from one output at a time. This is unusual (and a poor design), but I recall having this problem previously.
It could also be a problem with the cables and/or adapter
that you're using. Try using a different cable/adapter and disconnecting one of the two outputs to see what happens.
There may also be a menu setting in your DVD player that may act as a switch (of sorts) and mutes the audio from that output jack.
You may want to consider testing another DVD player in the same scenario.
There's also the remote possibility that the receiver itself is defective. If it was purchaeed recently, perhaps it can still be exchanged?
Good luck with resolving this problem!