Unity Tree Brush tool is not placing tree models

I imported Tree models from gtrader.com into unity and add textures to them. When I try using the tree brush in the Terrain section it will not place down trees. I can place my tree is normally by dragging it out into the scene. Most of the trees are OBJ and FBX.

You have to set the model/prefab that you want to be the tree in the object holder first