Value doesn't change in game when updated.

I have two scripts one called score, which calculates the score then converts it to a string. The other script is called Score Multiplier, that updates the multiplier value in the score script when I pick up the multiplier object.

Score Script:

 public float score = 0.0f;
     public float defaultScore;
     public float multiplierScore;
     public float multiplierNum = 0;
     public TextMeshProUGUI prefab;
     
     void Update()
     {
         defaultScore = Time.deltaTime * 15;
         multiplierScore = defaultScore *= multiplierNum;
         score += multiplierScore;
         prefab.text = ((int)score).ToString("0000000");
     }

Score Multiplier script:

 public GameObject pickupEffect;
     public GameObject Score;
     public float duration = 10f;
 
     
     public void OnTriggerEnter2D(Collider2D other)
     {
         if (other.CompareTag("Player"))
         {            
             PickUp();
         }
     }
 
     public void PickUp()
     {
         Instantiate(pickupEffect, transform.position, Quaternion.identity);
 
         Score multiplier = Score.GetComponent<Score>();
         multiplier.multiplierNum = 1000;
 
         Destroy(gameObject);
     }

So when the player collides with the multiplier object the multiplierNum float value should update to 1000. Instead the value updates when I restart the game or when I die and respawn.

This is the respawn code in the player controller:

 if (health <= 0)
         {
             SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);
         }

I just started using unity and coding about 4 days ago so please make your responses nood friendly.

Thanks.