Increase maxHealth at Healthbar

My problem is that when I add 100 HP to the enemies from Stage 10 onwards, i.e. 200 HP, the health bar only moves from 100 HP.

I can also set maxHealth to 200 and maxHealth remains at 100.

Does anyone know why this is so?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
 
 public class EnemyTest : MonoBehaviour
 {
     public int maxHealth = 200;
     public int currentHealth;
     public static int goldCount;
     public int Mob;
     public int internalGoldCount;
     public HealthBar healthBar;
     public Text GoldStats;
     public Text GoldStatsShop;
     public Text Stages;
 
     public GameObject clickFX;
 
     public GameObject Spawning;
     public Transform SpawnPoint;
     public GameObject[] enemies;
 
     void Start()
     {      
         Spawn();
 
         Mob += 1;
 
         internalGoldCount = goldCount;
 
         currentHealth = maxHealth; //current life
         healthBar.SetMaxHealth(maxHealth); //Sets the bar to maximum life
     }
 
 
     void Update()
     {
         GoldStats.GetComponent<Text>().text = "" + goldCount;
         GoldStatsShop.GetComponent<Text>().text = "" + goldCount;
         Stages.GetComponent<Text>().text = "Stage " + Mob;
 
         if (!EventSystem.current.IsPointerOverGameObject())
             if (Input.GetMouseButtonDown(0))
             {                      
                 RaycastHit2D hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), Vector2.zero); //Mouse triggered on Enemy
             
                 if (hit.collider.gameObject.CompareTag("Enemy"))
                 {
                     Instantiate(clickFX, SpawnPoint.position, SpawnPoint.rotation);
                     goldCount += 1 + Upgrades.MoneyPerClick;
                     currentHealth -= 1 - Upgrades.DamagePerClick;
                     healthBar.SetHealt(currentHealth); //Updates the bar
 
                     if (Mob >= 10)
                     {
                         maxHealth = 200;
                         healthBar.SetMaxHealth(maxHealth);
                     }
 
                         if (currentHealth <= 0)
                         {
                             AddGold();
                             Destroy();
                             Spawn();
                             Mob += 1;
                         }
                 }
             }
     }
     public void AddGold()
     {
         goldCount += 100;
     }
 
     public void Spawn()
     {
         int randomEnemies = Random.Range(0, enemies.Length);
         Spawning = (Instantiate(enemies[randomEnemies], SpawnPoint.position, SpawnPoint.rotation));
         currentHealth = maxHealth;
     }
 
     public void Destroy()
     {
         Destroy(Spawning);
     }
 }