I spent an hour getting 1k wood with my fists, maxed out the furnace with the wood, and..... nothing? I didn't see where the NPC spawned. And how do I open the door?
Did you have "chill grinding mode" enabled? I found a bug with that that would cause what you described.
If that's the case, as a temporary fix you can disable the setting, make sure the furnace is filled until it shows "ON" on the display, and then re-enable the setting.
I'm working on fixing it properly and will try to release the fix later today.