Challange 2: once add random to spawnInterval only 1 ball spawns,Once I added the Random spawn interval for Challange 2 the spawn only happens once.

Heres my code, I checked with the solution and it seemed to check out but when I add the randomness to spawnInterval the ball only spawns once then stops spawning. I dont really understand why.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class SpawnManagerX : MonoBehaviour
 {
     public GameObject[] ballPrefabs;
 
     private float spawnLimitXLeft = -22;
     private float spawnLimitXRight = 7;
     private float spawnPosY = 30;
 
     private float startDelay = 1.0f;
     private float spawnInterval;
 
     // Start is called before the first frame update
     void Start()
     {
         InvokeRepeating("SpawnRandomBall", startDelay, spawnInterval);
     }
 
     // Spawn random ball at random x position at top of play area
     void SpawnRandomBall ()
     {
         // Generate random ball index and random spawn position
         Vector3 spawnPos = new Vector3(Random.Range(spawnLimitXLeft, spawnLimitXRight), spawnPosY, 0);
         int ballIndex = Random.Range(0, ballPrefabs.Length);
 
         spawnInterval = Random.Range(2f, 5f);
 
         // instantiate ball at random spawn location
         Instantiate(ballPrefabs[ballIndex], spawnPos, ballPrefabs[ballIndex].transform.rotation);
         
     }