I can't get my spawner to work! pls help fast.

Hello. i'm new to programming and i am trying to program a simple dodge game. i can't get my spawner to work an i dont no why. if you can help me it would be very nice.

Here is the code

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class WaterDropSpawn : MonoBehaviour
 {
 
     public GameObject WaterdropPrefab;
     public float respawnTime = 1.0f;
     private Vector2 screenBounds;
 
    
     void Start()
     {
         screenBounds = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height, Camera.main.transform.position.z));
         StartCoroutine(dropWave());
     }
     private void spawnEnemy()
     {
         GameObject a = Instantiate(WaterdropPrefab) as GameObject;
         a.transform.position = new Vector2(screenBounds.x * -2, Random.Range(-screenBounds.y, screenBounds.y));
     }
     IEnumerator dropWave()
     {
         while (true)
         {
             yield return new WaitForSeconds(respawnTime);
             spawnEnemy();
         }
     }
 }