Pause Menu not working

I was following a Brackey tutorial for a simple Pause Menu. The problem is that even though I have implemented the code as said in the video, it would not appear and would crash my project. Any solutions? P.S this is the video:https://www.youtube.com/watch?v=JivuXdrIHK0 and this is the code:

using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI; using UnityEngine.SceneManagement;

public class PauseMenu : MonoBehaviour {

 public static bool GameIsPaused = false;

 public GameObject pauseMenuUI;

 
 void Update()
 {
     if (Input.GetKeyDown(KeyCode.Escape))
     {
         if (GameIsPaused)
         {
             Debug.Log("game is paused");
             Resume();
         }
         else
         {
             Pause();
         }
     }
 }

 
 public void Resume()
 {
     pauseMenuUI.SetActive(false);
     Time.timeScale = 1f;
     GameIsPaused = false;
 }

 
 void Pause()
 {
     pauseMenuUI.SetActive(true);
     Time.timeScale = 0f;
     GameIsPaused = true;
 }

 
 public void LoadMenu()

 {
     Time.timeScale = 1f;
     SceneManager.LoadScene("Main Menu");
 }

 // Quit game exits the game
 public void QuitGame()
 {
     Debug.Log("Quitting game...");
     Application.Quit();
 }

}