why isn't OnCollisionEnter called?

so in FeetScript in footmesh_R i have

    void OnCollisionEnter(Collision collision)
            Grounded = true;

but even though i drop Testingpants on a mountain oncollisionenter is never called. i have tried with breakpoint and debugger and you can see Grounded is still false in the inspector. but the physics are working there is no other collider stopping Testingpants from falling through the level.

the mountain is a static mesh collider and for the foot i have tried both convex meshcollider and boxcollider. - same result

i have now tried with 2 boxcolliders as well still no call.

You need a rigidbody on both colliders.

Set constraints if you don’t want it to jump around.

You have Static collider on the mountain.
OnCollisionEnter is for Rigid Bodies ,i.e., gameobjects which have a Rigibody Collider.

Therefore, as @TheMiningSheep said, you need Rigidbodies on both game objects.