I just setup my old AppleTV 3 in the bedroom but for some reason I can't get it to play my movies and tv shows from Plex. I'm using my iPhone X with iOS 11 to stream from via AirPlay. When I choose the AppleTV 3 the screen goes dark 2 times and then it just stays on the app screen on the AppleTV 3. The iPhone app looks like it is still trying to play the movie via the AppleTV 3 but it never does. I have also tried from my girlfriends iPhone 7 and from our sons iPad, but nothing seems to work?