How do I get the enemies to damage the player?

It used to work. But then I swapped what I had for a Player to a FirstPersonController for menu reasons. Then I entered the main scene to find out that the enemies no longer damage the player.

using UnityEngine;

public class SendDamage : MonoBehaviour { public int damage;

 private int setDamage;

 private void Start()
 {
     damageOutput();
 }

 private void damageOutput()
 {
     setDamage = damage;
 }
 void OnCollisionStay(Collision other)
 {
     if (other.transform.CompareTag("Player"))
     {
         other.transform.GetComponent<PlayerDamage>().ApplyDamage(damage);
     }

}

the Enemy SendDamage Script.

using UnityEngine; using UnityEngine.UI;

public class PlayerDamage : MonoBehaviour { public Text healthPanel; public int health = 100;

 // Start is called before the first frame update
 private void Start()
 {
     healthPanel.text = health.ToString();
 }
 public void ApplyDamage(int damage)
 {
     if (healthPanel != null && health > 0)
     {
         health = health - damage;
         healthPanel.text = health.ToString();
     }
 }

}

and the Player Health script