Had a new operator cause this problem.
By pressing buttons caused the machine to go in MACHINE LOCK.
Have MACHINE LOCK button undone by cutting wire to it.
Have replaced the I/O board with no luck.
looking for ideas?
Had the same trouble with a Doosan 550, the problem began when a operator switched the machine off while the machine lock was switched on. Only way to switch it back off after powering up was to switch the function off by way off a Keep Relay. What make and model is your Machine?