hallowed fields doesn't work in ID

[Zeyphor]

recently, DG triggered the halloween event
since then, I hadn't seen any hallowed ghosts, and then, a few floors after it was triggered, I found the hallowed fields, but it seems that I can't enter them because "You do not understand how to activate the portal. Maybe look for clues elsewhere..."
EDIT: after passing the portal to a different part of ID, I entered the pikacataclysm and found a hallowed ghost there; now I have the quest, but will probably never see that halloweed portal again