How do fix my pause menu

I have a tower defense game I'm working on and have 4 levels with a pause menu that can toggled and within the pause menu I have a retry button that is supposed to reload the level scene and restart the level. the level starts with a enemy wave countdown before the enemy spawns, when the retry button is pressed it will reload the scene but the 1st wave countdown of the level after the retry button was pressed it won't start. I'm not to sure why that is case as all other player interactions work properly, its just the wave countdown that doesn't start.

This is my pause menu script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 
 public class PauseMenu : MonoBehaviour
 {
     public GameObject pauseUI;
 
     public GameObject playerPanelUI;
 
     public GameObject shopPanelUI;
 
     public string mainMenu = "MainMenu";
 
 
     // Update is called once per frame
     void Update()
     {
         if(Input.GetKeyDown(KeyCode.Escape) || Input.GetKeyDown(KeyCode.P))
         {
             Toggle();
         }
     }
 
     public void Toggle()
     {
         pauseUI.SetActive(!pauseUI.activeSelf);
 
         if(pauseUI.activeSelf)
         {
             Time.timeScale = 0f;
 
             playerPanelUI.SetActive(false);
             shopPanelUI.SetActive(false);
         }
         else
         {
             Time.timeScale = 1f;
 
             playerPanelUI.SetActive(true);
             shopPanelUI.SetActive(true);
         }
     }
 
     public void Retry()
     {
         Toggle();
 
         SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);
     }
 
     public void Menu()
     {
         SceneManager.LoadScene(mainMenu);
     }
 }

This my Wave spawner script my wave countdown is attached to this script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 
 public class WaveSpawner : MonoBehaviour
 {
     public Transform enemyPrefab;
     public Transform spawnPoint;
     public float waveInterval = 5f;
     public float countdown = 2f;
 
     private int waveIndex = 0;
 
     public Text waveCountdown;
 
     public Wave[] waves;
 
     public GameManager gameManager;
 
     [Header("How Many Enemies Are Left")]
     public static int EnemiesAlive;
 
     void Update()
     {
         if(EnemiesAlive > 0)
         {
             return;
         }
 
         if (countdown <= 0f)
         {
             // The coroutine will pause execution and automatically
             // resume at the next frame
             // With coroutines we begin to model behavior without affecting performance
             StartCoroutine(SpawnWave());
             Debug.Log("Wave Start");
             countdown = waveInterval;
             return;
         }
 
         if (waveIndex == waves.Length)
         {
             if (EnemiesAlive < 1)
             {
                 this.enabled = false;
                 gameManager.WinLevel();
             }
         }
 
         countdown -= Time.deltaTime;
 
         waveCountdown.text = string.Format("{0:00.00}", countdown);
 
         countdown = Mathf.Clamp(countdown, 0f, Mathf.Infinity);
     }
 
     /// <summary>
     // IENumerator allows for this function to pause before being execute
     // in this case we want out waves to spawn incrementally
     // On top of this function running incrementally
     /// </summary>
     /// <returns></returns>
     IEnumerator SpawnWave()
     {
         PlayerStats.Waves++;
       
 
         Wave wave = waves[waveIndex];
         for (int i = 0; i < wave.count; i++)
         {
 
             SpawnEnemy(wave.enemy);
             // the amount of time the function will pause given the IENumberator
             yield return new WaitForSeconds(0.5f);
         }
 
         waveIndex++;
     }
 
     void SpawnEnemy(GameObject enemy)
     {
         Instantiate(enemy, spawnPoint.transform.position, spawnPoint.transform.rotation);
 
         EnemiesAlive++;
        
     }
 }