Video won't show on iPad

Hi
I've made an animated info-graphic in Animate. Size 1280x720 at framerate 29,97.
I then export as video, which generates a .mov file and automatically opens the mov in Media Encoder.
I press the green play button in upper right corner, and Media Encoder makes a mp4 file for me.
The file is placed on the server along with an HTML with the Bootstrap responsive embed code.
This works fine on all devices - except iPad
I tried other presets i.e. 'YouTube 720p HD' but nothing solves the iPad problem.
What to do?