Was the machine simply switched off and left unused or was move into storage ?

If its been stored in cold damp conditions
check the wiring for damage and connectors and Z axis stepper motor for corrosion


what's the stepper driver part number ?

first I would search for the stepper driver data to see what the fault LED could be indicating
( motor stall , over temperature , internal driver fault ? )

once your sure the wiring is OK
I would try connecting the Z axis motor to the spare driver

John