I'd been stuck at Chief Serpent Sgt for a while. I figured I needed to beat the story to unlock the next quest to continue advancing, which I still haven't gotten around to doing. Yesterday the quest wasn't available. Today, suddenly, it is. The only things I did were FATEs on WHM and ACN to get to 40 & 25, respectively, and did the quests for those levels; ran Haukke with FC; and did a bunch of Leves on MNR and BTN. Somewhere in there I did something to activate the quest. And I've no idea what.

Either that or they changed the pre-reqs with the update.