i am having the same issue. i was able to watch the same exact file a few days ago and now i can’t. also if i launch the file directly using media player it works just fine on the server. something must’ve happened in update. got latest today and it still didn’t fix it. some mkv files play others do NOT. also worth noting if you launch the video via plex app on my phone it plays the video but then has no audio. i just watched this show the other day and it played fine.