Try disconnecting the cable that leads to the 5 or 6 switches for coolant, chip conveyor, MST lock, TLM I think. Usually those switches are located on the side of the op panel. See if that does the trick. Sometimes one of them shorts out and messes up the PLC. Usually the coolant switch or converyor switch. Just disconnect it from the MC201 or key board and see if the key board starts working again.