Movie works on OSX, shows black screen on IOS or tvOS. Do different player support different codecs?

I run Plex on a Synology NAS so there’s no transcoding. I tried watching David Cameron’s The Abyss Extended edition, and it works fine on my laptop but on IOS (Ipad and Apple TV 4) I only get a black screen while the sound works. Seems to be x264 with DD5.1.

Any ideas?