Thanks boggart. Found it. Valefor's lair only refilled on the 3-hour area-boss timer, so after someone killed him the room stayed empty, and the Demon's Doorway had already used up your coin from Shumi on the way in. (Using the coin up is how the original works: the quest says you enter "using the Large Model of a Coin you received from Shumi".) What was missing: the original also summons the demon the moment a player walks in, if he isn't already there. That's now ported for all six demon lairs (Valefor, Andras, Marbas, Amdusias, Crocell, Astaroth), and you'll see "Valefor has appeared!" when he spawns.

Sukebe: a replacement coin is waiting in your Duey/delivery inbox from Maple Administrator. Claim it, talk to the Doorway, and Valefor should be there. The server fix is pushed but NOT live yet; it ships with the next server deploy. If you go in before that, he'll only be there if the room's 3-hour timer has come round.

Thanks for the report! The demon lairs (Valefor, Andras, Marbas, Amdusias, Crocell and Astaroth) now have their demon waiting for you whenever you step inside, instead of sitting empty. This is LIVE now.