I am thinking if I was forced to remove the last segment of HkG to KUL, can I add it back on after ticketed with Korean Air?

I did a round trip search, the whole itinerary popped up. It just did not have any j award on the outbound but stopover HKG and continue to KUL, then return from HKG with Korean showed up as 60k . It seems bootable and could not understand why I was told by the agent I need to drop Kul to make it work.