Afraid i am a bit of a mental midgit when it comes to AV stuff(too many buttons, too many cables and too old), but i have the BDP-360 and same Denon 1910 and recently when i play a blue ray disc i get picture and no sound.
It takes much cursing, switching on and off, un-plugging and plugging back in the HDMI cable, changing the source and back again and so on, until i eventually get the sound back.
No idea what is really going on here, maybe similar to your issue. Last time to get the sound i pushed the small on/off button next to the big on/off button.
Drives me nuts.
Interested to learn a solution here.