AppleTV, 3rd gen HD I believe.
Identify your Apple TV model - Apple Support
Find your Apple TV model number - Apple Support
As the Apple TV (3rd generation) [A1427 or A1469] supports SDR at 1080p, verify that your videos have these matching properties (or less) — not HDR, not 4K.
As the Apple TV (3rd generation) [A1427 or A1469] supports H.264 video, verify that your videos have this matching property.
As the Apple TV (3rd generation) [A1427 or A1469] supports AAC (or AC3 audio), verify that your videos have these matching properties.
Apple TV (3rd generation) technical specifications - Apple Support
Media files with other codecs may need to be converted.
The TV app on Mac may have ditched support for some older codecs, so verify that all the media in the playlist (still) plays on Mac in the TV app as well.
Playlists should continue to work, unless one of the files in the playlist has a compatibility issue with one of the apps involved with Home Sharing or AirPlay.
- Finder’s Get Info window will give some codec details.
- QuickTime Player’s Movie Inspector window will give some codec details.
- Invisor Lite (or any analyses tool based on MediaInfo) will give extensive codec details.
