Videos in My Tivo Recordings Folder Not Appearing in Transfer Apps

I have a laptop running windows 8.1 and when I add non .tivo/.mpeg files to the My Tivo Recordings folder they don't show up in Tivo Desktop Plus or pyTivo. On my old laptop with windows 7 I can still transfer .avi and .mkv files to the tivo without a problem. I assumed it was a Tivo Desktop issue but pyTivo doesn't see them either. Any ideas?