Thanks, Angelo. I was just curious why one file would work and the other did not. I'm uploading the files to my S3 area via Chrome and the regular S3 upload method. I'll do some more testing to see what the different is between the two files. The meta tag for each one is the same - application/octet-stream.
Update: Oddly enough, I used the Cloudberry Explorer to upload the file to my S3 container. It set the meta data as video/mp4, but my CloudFront link still threw the error. However, if I used the actual S3 link, PowerPress took it with no problem. It seems to indicate some strange CloudFront issue or something else I just don't quite understand yet.