Video Clip Resolution

I have a video Player component that loads a video file but I struggle to load larger files.

I’m using .mp4 with h264 codec.

1024x1024 works
1200x1200 doesn’t work
1280x720 works
1920x1080 works
2048x2048 doesn’t work
3840x2160 doesn’t work

What is the problem here? I can play all files with QuickTime but not in Unity.
I also tried using AppleProRes but it didn’t work for any resolution.
Are there any other formats I should try.

I tried it yesterday on a different machine and it worked in 3860x2160.
That machnine is running windows 10 but I don’t think that should matter.

Can noboy help me here?