I got this module last week and I have some issues with it.
When plugged in MP3 mode where I only use Arduino UNO to supply power it didn't work with 3.3V pin but played alright (with all the buttons working) with 5V which shouldn't happen. I am using 32ohm 0.25W speaker, maybe that's why? But then again, I plugged some earbuds to it and again it was only working with 5V connected to it.
When I connect the device in 2 pin mode, I only get a "click" sound when playVoice functions are being called, but get no music whatsoever(neither 3.3V or 5V plugged). I get a strong feeling that it's not receiving a right command and tries to play a file that doesn't exist. I have ad4 files names 0000, 0001, 0002 etc, I was using the test files and my own but to no avail...
I hope any of you have some more ideas