The hot fix notes say that existing keys should allow you to skip to the end of the quest now. Might try dropping it and retaking it. If that doesn’t work than maybe a ticket is warranted.
I was in EA and had already gotten keys and used one after completing a bountiful delve.
I got this quest after global launch, and the previous key counted (before the listed hotfix) I just had to run another bountiful delve to finish the quest, and I did NOT have to unlock the chest at the end.
Again, before the hotfix, I didn’t need to get another key, a previously used key counted for me, just had to run a delve. Kind of like getting a delver’s call quest after having run the delve- you have to run it again to count.
Can’t speak to how the hotfix changed things but my second toon picked up the quest after my main had already done it and I was able to complete the quest immediately.