on trigger enter 2d not working

ok so I did everthing I was supposed to do everything has 2d box colliders and it is all tagged, take a look and the debug.log did not show up

     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
     
     }
     void OnTriggerEnter2D(Collider2D other){
         Debug.Log ("hi");
         if (other.gameObject.tag == "enemy") {
 
             Destroy (other.gameObject);
 
         }
 
     }
 }