Why won't the detergent cup lid latch closed?

The detergent cup lid will not latch if the dial is not in the OFF position. Turn the dial to OFF and slide the door latch to the left before adding detergent and closing the main cup. If the detergent cup has already been closed and needs to be reopened, turn the detergent cup handle counter-clockwise until it releases — a snapping sound may be heard. (Page 24)