I just chanced upon this. Sorry that I didn’t notice it earlier. If you’re still looking for a hint, try this:
GIVE KEY in the inn. You can now talk to the villagers. (What has giving the key to the innkeeper got to do with the villagers? Your guess is as good as mine.)
TALK VILLAGERS. You can now enter the church. (Once again, what has talking to the villagers got to do with the church a couple of rooms away? No idea.)
Finally, USE BELL or RING BELL at the church and someone opens the door from the inside.
If you’re still having trouble, I see that @dfabulich has provided some comprehensive invisiclues at "The Curse of Rabenstein" Invisiclues Hints