Tree Colliders not working

I have prefabs with trees that have capsule colliders, when placed individually they work and I am not able to walk through them, but when I import them into the terrain component and mass place them, the colliders no longer work, any idea on why and how to fix?

The problem was I had too many trees on my terrain (I had a 3000 x 3000 terrain with 200,000+ trees that my computer could handle) but it instead caused the PhysX engine to crash, disabling tree colliders.