Have you already replaced the Pump Assembly? and now the printer won't allow you to reset it? OR you were simply hoping to reset the old pump assembly to new again, as you have done in the past?
The manual reads:
Whenever the PUMP, CAP, ASSY., is replaced, the corresponding
adjustments must be carried out. See Chapter 5 "ADJUSTMENT"
1. Reset When Pump Motor Change
Indicating you need to actually replace the pump assembly to be able to perform this adjustment.