Finished the mission but can't get the reward~~

Hi Suensiuhong. We believe this is currently a bug with the quest, which we hope to fix in the near future.

Unfortunately there's not much we can do until it's fixed sorry :( We don't have the means to generate items in the live realm.
In the meantime you might be able to find a generous soul in-game who could provide you with the skill-gem normally part of this quest. Our Item Showcase forum also have free giveaways on a regular basis.