Way back in August, Plex announced that you no longer need a Plex pass for the Xbox 360 player: ( https://blog.plex.tv/2015/08/25/graduation-day-the-roku-and-xbox-360-apps-are-now-free-for-everyone/ ). However, despite having the latest version of Plex for the Xbox 360 (I even tried downloading it again), the Plex app says I can’t sign in, because I don’t have a Plex pass, and then goes on to say that it’s a technical preview. I don’t understand why this is happening would it be because of my geographical location (I live in the UK)
Before the PLex app on the Xbox360, I used to use the Xbox Video app to access the videos on my plex server. Plex should appear as a folder on the Xbox video app. Maybe that work for you.
