Check all the PCB boards inside, they have all red diodes which mean that the power supply is OK. Had once a problem on ZAPPI board which is inside this truck. The "computer" flat-cable going from master board to slave board was broken where the cables were soldered on the board. We soldered back and the truck started to work.
The message on the panel was "slave not connected". What message do you have on the panel where the driver is working ?
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