Well to me it starts to look like the board is defective, might be that there's bad connection somewhere and the motor cannot move as one of the phases doesn't work (or something...). Of course you could try to re-flash the firmware if not already done so. Also check for bad solder joints on the Z-pins. I don't recommend trying to remove the heatsink that's on top pf the stepper drivers, I'm assuming there's some kind of warranty on the printer.
Are the other boards are working?