The quest “A Greedy Goblin’s Paradise” is not spawning the Void Portal to follow Umbric into the Atal’Dazar scenario to complete the quest.
Umbrik will act out the animation as if he is summoning the Void Portal, however, he just fades out without the portal ever appearing.
I have attempted logging out/in, relaunched the client numerous times, as well as abandoning the quest/picking it up again, but my efforts were to no avail.
Note: Entering the instance does not trigger any quest mechanics or dialogue, nor is Umbrik in the instance itself.