Open Door on all enemies dead?

I want to trigger an animation to open the door when I kill all enemies in a given arena, and I briefly had it, but then it stopped working, not sure why.

Here is the script I have so far:

 public class Door : MonoBehaviour
 {
     public Vector3 halfDimensions;
     public Vector3 boxCenter;
 
     public LayerMask layerMask;
 
     public Animator anim;
 
     private void OnDrawGizmos()
     {
         Gizmos.DrawWireCube(boxCenter, halfDimensions);
     }
 
     // Update is called once per frame
     void Update()
     {
 
         Collider[] enemiesRemaining = Physics.OverlapBox(boxCenter, halfDimensions, Quaternion.identity, layerMask);
 
         if (enemiesRemaining.Length == 0f)
         {
             Debug.Log("Arena Cleared.");
             anim.SetTrigger("Opening");
             anim.SetBool("Open", true);
         }
 
         //if (!Physics.CheckBox(boxCenter, halfDimensions, Quaternion.identity, layerMask))
         //{
         //    Debug.Log("Arena Cleared.");
         //    anim.SetTrigger("Opening");
         //    anim.SetBool("Open", true);
         //}
     }
 }
 

the part I commented was something I tried before but didn't work. What am I doing wrong?