"No Audio Content" in iTunes via Plex and DTS Play-Fi

I am trying to play music from iTunes on my iMac home computer.  I have loaded Plex as a music server and use my iPhone or iPad to access the DTS Play-Fi app.  I have Plex showing up in my DTS Play-Fi app, but when I access the media server, then iTunes it says, " No audio content".  It shows the music and album artwork, but when I try to play it I get the error message above.

Any suggestions?

Thank you