Thanks Dae—that gave enough information to figure it out.
Apparently onedrive sometimes shortens overly long file names. In this case, it shortened not only the filename, but the extension as well. This was causing windows to think that the extension was .COL, even though the extension was actually .colpkg in the file.
Moving the impacted files out of onedrive made the files accessible again.
Many thanks 
No idea why onedrive did this to only some of the files.