Maybe the guitar is set to stereo so there´s no sound. Press (and hold) the piezo pot for 10 seconds and see the blue light flashing, if it flashes once, the guitar is set to mono. If it flashes twice is set to stereo.
I stell have the same , problem! Whem i put the 3 baterries, but in mi case led dont flashe and theres not a sond out put.
Please I need help. Im in Brasil What can i do?