Terrain Trees not Creating Meshes, only Billboards

I created a tree in blender, one mesh, 2 materials. Applied transformations and imported into Unity. I then placed it in my scene, added a collider, and dropped the tree into an empty prefab. Made my brush, dabbed it on my terrain, and... nothing but billboards. The trees literally vanish when I get close to them, though I can still walk into them.

I dragged my prefab into the scene, and my tree does appear just fine there. My tree has less than 700 verts, my max mesh is set to 3000 something.

The only setting that affects anything is moving the billboard distance closer. I then can manage to generate some lovely 2D cutouts for trees... not what I want though.

All help is appreciated, thanks.