Ive just gone through and marked off each of the 16 and the water hasnt drained in the cave to allow me all the way down. So I can't start the workd quest :l

Which underground cave where i can meet with 4 aranara?

The quest didn’t unlock for me automatically either after the 16th. But I returned to where the 4 Aranara are in the underground cave and it immediately triggered the quest. Hope this helps.

As of now, I also do not have access with the quest, despite finishing all 16 pillars (I marked them down as well so I won't forget which one is which).

My problem was solved. After going through each of the stone seal again there's one mech that somehow re-sealed. Maybe the patch yesterday was for this bug?

I have the same problem as the other commenter. I've done all 16 of em and still havent got the quest

Even after unlocking 16 stone seal, I haven't got the world quests. I guess either I was missing some or maybe I should clear another quest first. If anyone found the reason please write it here.