This is the first real problem that I have ever had with plex in over a decade, but I am really stuck on this one. I am not exactly sure when the problem started, but I noticed last night while watching a movie that PMP (on windows 10) was not sending Multi-In to the receiver. I assumed some audio settings changed, but they were all correct. I had all passthrough options disabled, and I am relying on PMP to decode the audio as recommended. I tried multiple movies with DD5.1, DTS and DTS HD, but PMP was sending 2 channel audio for some reason. Strangely enough, once I enabled all of the passthrough settings (which i realize is not recommended), then everything worked perfectly. Any idea what could cause this issue and how I can troubleshoot?
Check the Windows Sound settings and make sure the receiver audio device is configured for 5.1 or 7.1 channels.
Thanks for the help. Some windows or driver update changed my Denon AVR config in windows to 2 channel. I changed it back to 5.1 and all is well again.