From time to time the Handheld Nautiz X4 turns black and it can not be turned on or restarted.
We seen this happened a few times. It was suddenly not able to be turned on. No red light would show on the indicator light when plugged in to a charger. Swapping chargers or batteries had no affect.
Though we don’t know what causes this, but the steps in this link could help. I tried it several different ways on the first handheld that was sent back, with the battery in, without, with the battery door on and off. After the 5th attempt the handheld came back on.
Press the blue and red key at the same time for 8-12 seconds:
This will disconnect the backup battery and after this the unit should start up.