Hi, its about Toyota electric forklift, model 7FBMF25

I have a situation with customer's forklift vehicle. Battery was accidentely charged in reverse polarity and then plugged in vehicle and turned on. When the key was turned ON, the command display lighted on a moment and then blank. After that, no contact. Parking brake is still stuck. Battery was charged correctly after that but same simptoms. No contact althought baterry now shows 86 Volts. I checked fuses that are just beside the main controller unit but they are OK.
What could posibly happen? Is there any kind of reverse polarity protection before the main controller, like polarized capacitor or something?

Thanks