IE is very picky about video. It’s also a piece of garbage, and belongs in the browser garbage bin along with Safari. But I digress.
IE requires MPEG4 video in H.264 compression. Not x264, and webm is supported with a plugin but not by default. But that’s not all!
From https://lars.st0ne.at/blog/html5+video+in+IE11+-+size+does+matter
Finally I’ve found the following link MS H.264 Decoder. The site describes, that the Microsoft H.264 Decoder (Windows 7) supports a maximum resolution of 1920 × 1088 pixels.
It might actually be even less than that. IE was unable to display a video in one of my projects at 1920×1036. I recompressed it down to 1334×720 and magically everything was fine.