Cube falls through custom plane

So im trying to figure out why my cube (player) wont stop falling through my ground (custom low poly plane from blender). My Cube got the mesh colllider and ive tried like 5 diffrent colliders on my ground but it keeps on falling through!!
Ground:

Cube:

 

For the cube, use a box collider instead of a meshcollider (although it will also work) but you need to check the convex flag on your mesh colliders.

 

You also need a RigidBody in some of your colliding objects in order for the collision to register. So check that too.