Unable to upload video mp4 files

The bug has been fixed in the latest software version....V 10.1 Camera  Raw 13.1

Are they HEVC files using the H265 codec? Lightroom Classic on windows does not support those: https://helpx.adobe.com/lightroom-cc/kb/heic-files-support.html#hevc-video-files

Try this: http://www.lightroomfanatic.com/tutorials/troubleshooting/solving-lightrooms-there-is-a-problem-with-the-video-file-error/

What happens if you change the file extension to .mpg?

not LrC, but  see: https://windowsreport.com/file-unsupported-compression-type/

followuo, apparently thaat might not be the issue/solution,

not a solution,  but see: https://community.adobe.com/t5/lightroom-classic/cannot-import-mp4-files/td-p/10956262?page=1