Trying to clear the dungeon, but...

I can't find the "Advanced Elemental Classroom" in the "Water Nation"! 💦 I finished building the "Elemental Studies (Classroom)" but it didn't count as clear, so I guess it's something else... I posted in the gathering hall too, but since I can't upload screenshots there, I'm posting here as well 😌💦 (Update) Just as I was saying that, I cleared it successfully! Maybe it was a time lag?