When the lights don’t work, check the steps in lights are not working.

1: Set the multimeter on DC (direct current)
2: The red pin must be placed on the + of the battery and the black pin on the –
3: Read the measured voltage on the multimeter

Warning: don’t touch any other metal parts on the pcb and don’t let the metal pins of the multimeter touch each other during measurement, this will cause short circuit and can damage the plant microbial fuel cell and the electronics. Be careful not touching the electronics by hand.