adding case 5

powerup.cs

 private void OnTriggerEnter2D(Collider2D other)
    {

        if (other.tag == "Player")
        {

            Player player = other.GetComponent<Player>();
            if (player != null)
            {
                //if powerUp ID is 0
                switch (_powerupID)
                {
                    case 0:
                        player.TripleShotActive();
                        break;
                    case 1:
                        player.SpeedUpActive();
                        break;
                    case 2:
                        player.ShieldsActive();
                        break;
                    case 3:
                        player.AmmoRefill();
                        break;
                    case 4:
                        player.AddHealth();
                        break;
                    case 5:
                        player.BigLaserActive();
                        break;
                    default:
                        Debug.Log("Default Value");
                        break;
                }
                Destroy(this.gameObject);
            }
        }
    }
}