Well, did this quest time ago, so i don't remember how i did it, Paellicia is the Arpi Girl and for the Snap you need the Atelier. So let's rule those out.
1.You already did maybe.
2.Have you tried to talk to him in a different time of the day.
3.Have you meet with Paellicia?
4.Have you defeaded Paellicia?
5.Have she moved to the castle.
6.Is the Castle develop enought, she goes to the tower, from the stairs to the west, if there is a ruble, probably you won't reach her or she wouln't move at all.
7.Have you build the Atelier in the backyard. You need it to take pictures.
Hope it helps