iTunes + AirPlay = no movies

[jacg]

Am I the only one having problems getting purchased movies to play via AirPlay? I've bought a bunch of TV programmes for teaching and I couldn't get them to play on 10.13.1 (I just got beachball and no video). I filed a bug report with Apple.

Now in 10.13.2 it is even worse. My main display goes grey. My pointer disappears and there's glitching as I move the invisible pointer around on my extended display (on the the Apple TV 4K). And now I get a warning about "The selected film won’t play on one of your connected displays." due to copyright reasons. These are all shows I purchased from Apple.

 

[jacg]

Ok, so further testing and a pointless call with Apple Support has shown that I have other AirPlay issues (in addition to HDCP issues, which even prevent purchased videos from playing on my own display while I have an extended desktop via AirPlay).

The Airplay button next to the volume in iTunes (both in the main window and any player windows) does not work. It does not show an accurate list of Apple TVs and it will not play to any of them. Other apps like Safari and Quicktime list and push video to AppleTVs fine.

Does this button work for other people? I've tried trashing every iTunes and AirPlay pref, and reset NVRAM with no effect.

 

[jacg]

SOLVED

After much testing, including another Mac, it turned out to be a problem with the 'Airplay Client Identity' keychain file. I quit iTunes, deleted the identity and iTunes now works with my Apple TV4K (and hopefully all other Apple TVs).