2D Colliders Not Working

Hello, I'm pretty sure I've done everything right to make my objects collide but they dont! My Project is a 2d project and has 2d mode on My games is where i have the player in the middle of the screen and enemies come at him. I have a shield thats moves when you touch a side of the screen. I want it so the enemies collide with the shield and explode (destroy).The enemies are instantiated so i added this script onto the enemy:

 void OnCollisionEnter2D (Collision2D col)
 {
     //Check collision name
     Debug.Log("collision name = " + col.gameObject.name);
     if(col.gameObject.name == "Shield")
     {
         Destroy(this.gameObject);
     }
 }

}

And i put 2d ridgidbody's and 2d box colliders on the enemies and the shield. The ridgidbody's are not kinematic, the gravity is just turned off. If this is just a bug in Unity then should I restart the project? Any help is greatly appreciated! Thanks!