My Plex Media Server has stopped running on my Nvidia Shield TV and I have not been able to turn in back on. I go into Plex Settings on my Shield, go to Plex Media Server (Stopped), turn on, wait while it says "Starting Server" but it still says stopped, It won't turn on.
Make sure you are running the latest version. There have been reports of the play store not listed the correct version. Try pushing the update from a web browser instead.