Hat Trick Game Tutorial: Balls are not Spawning...

Hi all,

I am working through the "Hat Trick" 2D Tutorial, and I am stuck on the GameController/Random ball spawning part. My code seems to mirror the tutorial exactly, but my balls aren't spawning. No compiler errors, so I'm kind of at a loss... I noticed there are parts of code in the Tutorial that are now deprecated, but it hasn't thrown an error for that either. Code posted below, thanks for the help:

 using UnityEngine;
 using System.Collections;
 
 public class GameController : MonoBehaviour {
 
     public Camera cam;
     public GameObject ball;
     public float timeLeft;
 
     private float maxWidth;
 
     // Use this for initialization
     void Start(){
         if (cam == null){
             cam = Camera.main;
         }
         Vector3 upperCorner = new Vector3(Screen.width, Screen.height, 0.0f);
         Vector3 targetWidth = cam.ScreenToWorldPoint(upperCorner);
         float ballWidth = GetComponent<Renderer>().bounds.extents.x;
         maxWidth = targetWidth.x - ballWidth;
         StartCoroutine(Spawn());
     }
 
     void FixedUpdate() {
         timeLeft -= Time.deltaTime;
     }
 
     IEnumerator Spawn ()
     {
         yield return new WaitForSeconds(1.0f);
         while (timeLeft > 0)
         {
             Vector3 spawnPosition = new Vector3(Random.Range(-maxWidth, maxWidth), transform.position.y, 0.0f);
             Quaternion spawnRotation = Quaternion.identity;
             Instantiate(ball, spawnPosition, spawnRotation);
             yield return new WaitForSeconds(Random.Range(1.0f, 2.0f));
         }
     }
 }