change music on a DFPLAYER MINI and speaker setup

I have a problem.
I’d like to make a program to change the music with a push button but it doesn’t work.
I’ve tested all the connections are good.
and I can play an mp3 file but I can’t change the mp3 file.
the equipment I use arduino uno, DFPLAYER MINI, speaker HP4028 and a push button
Have you a solution?

HAU_PARLEUR_TEST.ino (1.49 KB)