Apple TV 4K (2021), Dolby Vision profile 5, MP4 file won't play correctly

[Volts]

I haven’t looked at this in a while, so it’s possible things have changed, but MP4 dvhe is probably the problem.

Plex on the AppleTV uses the Apple player engine for Dolby Vision content.
Apple expects MP4 DV files to be muxed as dvh1, not dvhe.

There are a variety of ways to remux from dvhe to dvh1. The very best is probably MP4Box if you care to learn it.

Plex displays wrong colours with Dolby Vision on AppleTV 4k

There’s a lot of dvhe DV P5 content out there. Unless Plex makes a change I don’t expect dvhe to work on Apple TVs. Apple expects dvh1. Simply relabeling dvhe to dvh1 doesn’t work, because they should be muxed differently. The straightforward solution for dvhe is to extract the raw streams and mux them with MP4Box to produce an Apple-compatible dvh1. But that process is annoying when there are many streams. ffmpeg emits files with hvc1, which I think is incorrect behavior. But hvc…

Another option would be to remux into MKV files with MKVToolNix. Plex has made a bunch of improvements in the last year for MKV DV playback.

I prefer Apple-flavored MP4 dvh1 because they work elsewhere in the Apple ecosystem.