Make sure that you have no other quests that Jirosh takes part in active at the same time. If you have two or more quests that involve the same NPC, they will often conflict - and so you'll need to do one at a time.
If this is the only quest you have, or the only one that you are sure involves Jirosh, it could be that the quest simply timed out because you took a bit too long, so you may have to discard it and get it from Jirosh again. But since you already have what he needs, it should be simpler :}
