Games : Why won't the truffle move in to my house

I've made a house for him in my above ground mushroom biome. I can see the giant mushrooms in the background along with mushroom biome monsters. It has the same song so I know it is a mushroom biome. I made my house out of mud and put mushroom walls on. I have a work bench, table, and a chair. I also have torches. I Think it is suitable and it isn't close to the corruption or Crimson because other NPCs move into my houses. I've defeated the wall of flesh. I also have a large room for the truffle. Please help me figure out how to get the truffle to move in.