PSE 18 Organizer can't play some MP4 files

Not a big deal in the grand scheme of things, but my PSE Organizer can’t play one or more MP4 video files, while playing most of them without problem. It says “The selected file cannot be played because your system does not have the required compresser/decompresser(code) installed.” I opened it through Windows File Explorer and it played without problem in Windows Media Player, so I know the file is not corrupted. And the other videos that the Organizer opens okay were taken with the same camera. So I’m just curious if anyone has come across this before, or has any idea how to fix this. (I came up practically empty-handed with Web and Community searches; what I did find applied to Premiere Elements, not plain (?) Elements.)

(P.S. I tried deleting the file from the catalog and then copying it back in, but it still couldn’t play it.)
(P.P.S. They misspelled compressor.)