One problem I see straight away is "The content for the field "file" must not be more than 8000000 bytes." .. basically something less than 7.5 MB.
My 20 second video is 8.2 MB,,
So, I guess that is my first problem? is there a work around?
AND... maybe the most disturbing thing is after it fails. The "Play Media" item looks to have saved, the file name is there, but it just doesn't work. .. If the upload or save failed, it should not save the item or show some indication that it is not good to use.