Without any more information about how or with what software the playlist was created, it’s pretty hard to suggest or recommend a solution.
Did you populate the playlist from the files on the player, and not on your computer?
Did you place the playlist file in the same directory/folder as the song files are in? Many people mistakenly (but understandably) place the playlist file in the Playlist folder. That won’t work with .m3u playlists.
