Audio problem with new install

Hi, LibreELEC noob here. I just installed LibreELEC on my PC. I'm using the HDMI output from the motherboard into my home theater prepro. In the LibreELEC GUI I set the audio to go over the HDMI and the number of channels to 5.1 (my prepro is an old Denon and only supports 5.1). I can watch movies from my PLEX server in 5.1. But when I go to play my music files I get no audio. Any suggestions on what settings I can try? I'm an IT person so I have no problem with setting up an ssh session to my LibreELEC PC and using vi to edit files. Thanks in advance.

Nevermind. I plugged my LibreELEC PC into my receiver upstairs and audio works as expected. So I'm guessing it's a cable problem or something to do with the HDMI input on my Denon prepro.