Executing a function upon 2d collision

Hey guys,

I am working on a 2D Castle Defense game. I have a base with a polygon collider and a rigid body set to kinematic. Above it I have a square that has a box collider and a rigid body. The base has a function that decreases its healthbar. I want to run that function every time I get a collision with the square. I have tried using OnCollisionEnter, but it doesn't seem to work. Here is the code:

 using UnityEngine;
 using System.Collections;
 
 public class Base_Health : MonoBehaviour
 {
     public float maxHealth = 100f;
     public float currHealth = 0f;
     public GameObject healthBar;
     // Use this for initialization
     void Start ()
     {
         currHealth = maxHealth;
     }
     
     // Update is called once per frame
     void Update ()
     {
     
     }
 
    void OnCollisionEnter (Collision col)
     {
         if (col.gameObject.name == "Enemy")
         {
             decreaseHealth();
         }
     }
 
     void decreaseHealth ()
     {
         currHealth -= 2f;
         float calcHealth = currHealth / maxHealth;
         setHealthBar(calcHealth);
     }
 
     public void setHealthBar (float myHealth)
     {
         healthBar.transform.localScale = new Vector3(Mathf.Clamp(myHealth, 0f, 1f), healthBar.transform.localScale.y, healthBar.transform.localScale.z);
     }
 }

I appreciate any feedback.