Ha man, no offense but this is like airline tickets 101. If you ditch a sector earlier in the itinerary the rest cancels. Same holds for if you're on a longer ticket (say TPE-HKG-DXB-HKG-TPE). If you fly to HKG but then skip the Dubai sector the rest cancel as well.

Otherwise point of sale and various other price discrimination methods would be useless.

Sorry you have to learn the hard way. This is a no brainier unfortunately. Those two segments are tied together, and are priced as a unit.

If you want to skirt the system, you can sometimes ditch the final sector. Because the airline really doesn't have much leverage over you at that point, even though you've circumvented their pricing unit. But if they say "this fare is only valid for a return set of flights", which is the type of ticket you bought, and you ditch the FIRST sector, you realize they hold major leverage over you...aka that return segment. They enforce this leverage by cancelling the remaining segments. Which they are totally entitled to do (and will), and you aren't entitled to anything.

Sorry