I have a couple 4th Generation Apple TV's (non 4k). One is on the same network as my server and streams the files locally while the other streams over the Internet. The local Apple TV has no problem direct playing any of the files it supports. The Apple TV that streams over the Internet will not direct play any videos (regardless of codec/container) if is is over ~5 minutes. It just states "there was problem playing this video."
For testing purposes, I connected the usually local Apple TV to a hotspot so that it was streaming over the internet as well and it refused to direct play anything over ~5 minutes as well. I have used ffmpeg to cut some of the long videos down to short < 5 minute videos, while copying the codec and container, and it will play successfully.
I can successfully direct play videos in Chrome over the Internet, just not the Apple TV. Any ideas?