I’ve got the file. It came via FB Messenger and I downloaded it to my iMac. I wish the site would provide more error information. All it does is put a red stripe over the upload line and change the status to "Error". The file is 4.62MB in size, so it should be ok.
UPDATE: Well crap x2. I tried uploading as a .mov file - no joy. If anyone has any ideas, I'm all ears. Both files work just fine on the iMac.
UPDATE: Well crap x3. I tried loading both file types from a Windows 10 PC. Same thing.