Sonos wont play Plex content

Hi 
In the last week or so, Plex has stopped working in Sonos. You can see all the library items but the songs won’t play. I have done everything, including overhauling my network and doing a clean install of Plex on my QNAP NAS. I have spent days trying to troubleshoot this issue but so far, nothing. So I am wondering if anyone else might be having this issue, and has it been caused by a firmware update either on Plex side or Sonos? I have reached the point where I'm going to either have to ditch Plex or Sonos so that i can enjoy listening to my music without the hassle. I would really appreciate any advice that someone here might have. Thanks Jay