Terraria: Witch Doctor not spawning despite me killing the Queen Bee (in a friend's duplicate server of my world)

Solution 1:

It sounds like this is what happened:

1. You had your world file. We'll call it World A.
2. You copied your world file and gave it to your friend. We'll call that World A Copy.
3. You and your friend dug through the Jungle, then discovered and defeated a Queen Bee in World A Copy.
4. You went back to your own World A. The minimap shows what you did in World A Copy but the world itself does not match the minimap.

The information about whether you defeated a Queen Bee (or other bosses) is recorded in the world file, so you will need to defeat a Queen Bee again in World A.

Or you could have your friend give you the World A Copy file and replace your old World A file with it.

The reason the minimap does not match the world is because the minimap is stored with the player files, not the world files. Each world file has an internal ID number that connects it with a player's minimap files. Because you copied a world, both World A and World A Copy have the same ID number, so Terraria uses the same minimap for both worlds.