Image radial 360 Health Bar doesnt decrease

I have searched, and the others people similar situation doesn't helped me.

I have an Image UI radial 360 and it doesn't decrease when player loses health.

Here is the code:

 public class HealthBar : MonoBehaviour
 {
     [SerializeField] private float maxHealth = 100f;
     [SerializeField] private Image healthBar;    
     private float health = 0f;
     
     void Start()
     {
         health = maxHealth;
         healthBar.fillAmount = maxHealth;
     }
     public void UpdateHealth(float mod)
     {
         health += mod;
         if (health > maxHealth)
         {
             health = maxHealth;
         }
         else if (health <= 0f)
         {
             health = 0f;
             //Destroy(gameObject);
             healthBar.fillAmount = health;
         }
     }
     void OnGUI()
     {
         float t = Time.deltaTime / 1f;
         healthBar.fillAmount = Mathf.Lerp(healthBar.fillAmount, health, t);
     }
     void OnCollisionEnter2D(Collision2D col)
     {
         if (col.gameObject.tag.Equals("Enemy"))
         {
             health = health - 5f;
             healthBar.fillAmount = health;
         }
     }
 }