I guess If you don’t have the codec that the .mov file has been encoded with, this will not work. Especially if encoded with old codecs. On iOS, It seems only MPEG-4/h264 is supported in <video>. I am not an expert; I could be wrong, though.
I’m not sure what would be the best way to fix that.
For Chrome/Edge and similar, you should use video/mp4 for sure.
Honestly, it would be easier (universally compatible, at least) to convert MOV to MP4. 