Mesh Colliders not working on Android build

So here are all the details about my mesh.

Just imagine a car driving straight through the rock with no collision.

Basically it works in the editor and when I build to my android it stops registering and the car passes right through and does not collide.

I recently upgraded to 2019.3.4f1 and now the colliders suddenly don’t work when they where working before.

Are there too many polys on the mesh for android? All I can think of. Maybe the screenshots above will reveal something.

Thanks

Thanks for the replies. Turns out the model needed the read/write turned on.
See this post:
https://forum.unity.com/threads/mesh-collider-needs-transform-to-be-marked-as-readable-bug.414275/