Hello,
if SD-CARD is insert i and using switch 1 or 2 i get a buzzing noise but blue led is lighting for 0,5 sec after using the switches.
i use 3 different dfplayers and all of them have the same issue.
I turned of arduino to testing dfplayer alone and using it with a 3.3v or power adapter. but no luck.
At first i useit with 5v from arduino vcc and it worked for few days.
Here are two pics of wiring.
