DFPlayer Mini can't play/loop songs in folders

When using Getting Started code from: https://wiki.dfrobot.com/DFPlayer_Mini_SKU_DFR0299, if all of the music is in folders, then nothing plays.  If I have a file 001.mp3 at the top level, then the music plays, but arranged as in the following does not:

01/001.mp3

01/002.mp3

01/003.mp3

01/004.mp3

02/001.mp3

02/002.mp3

02/003.mp3

… etc.

Also, if I execute any of the folder commands from the Full Function example the play completes immediately (and makes no sound), and I get:

Execute 80 Play Finished!

Execute 81 Play Finished!

Execute 82 Play Finished!

Thanks,

-Kevin