OnCollisionEnter not working

As usual, OnCollisionEnter stops working at the tiniest little piece of dust that floats by. Well, here’s my code, very simple and SHOULD work:

function OnCollisionEnter(collider:Collision) 
{

if (collider.gameObject.tag == "ground")
{

Debug.Log("colliding with ground");

}
	
	if (collider.gameObject.tag == "layerPad")
	{
		Debug.Log("colliding with layer pad");
	}
}

Alright, layerPad has a rigidbody attached to it plus a box collider. The player has also has a box collider attached to it (no rigidbody (and no, I am not using any transform stuff)). Now when these 2 objects collide, they stop moving since they hit, but no debug.log. They have rigidbodies, they’ve got box colliders (both of the same type, they are both 3D colliders) the rigidbody is not a 2D one, I’m not using transforms, why the heck doesn’t it debug.log? Should’t this be working? (they are both marked as not to be a trigger). I’ve been stuck on this for THREE HOURS. It’s driving me nuts. Anyone have any ideas what I am doing wrong?

It’s fixed now. For some reason Unity wouldn’t collide with children objects. Big thanks to @Hikaros for pointing it out!
Here’s my finished code for anyone else with the same problem:

function OnCollisionEnter(collision:Collision)
{    
    if (collision.gameObject.rigidbody.position.x > rigidbody.position.x) 
    {
    	Debug.Log("right collide");
    } 
    else 
    {
    	Debug.Log("left collide");
    }

    if (collision.gameObject.rigidbody.position.y > rigidbody.position.y) 
    {
    	Debug.Log("top collide");
    } 
    else 
    {
    	Debug.Log("bottom collide");
    	if (collision.gameObject.tag == "layerPad")
    	{
    		ChangeTo(collision.gameObject.GetComponent(BounceScript).targetLayer, collision.gameObject.GetComponent(BounceScript).targetHeight);
    	}
    }
}