ES Group Impossible To Post A File With Mp4 Extension

Hi Friends,

I created a group https://www.yannanderson.com/en/friends/groups/dj-willow and I tryed to post a .mp4 video (but using FILE upload, because I can't upload videos on my site, because I don't have ffmpeg), but I have an error message, do you know why ? See attached picture :-)

Thank you for your precious help

Best Regards

Yann Anderson