unity don't display the next scene

and this is my script for Splash screen

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 
 [RequireComponent(typeof(AudioSource))]    // add audio source when attaching the script
 
 public class SplashScreen : MonoBehaviour
 {
 
     public Texture2D _splashScreenBackground;     //Creates slot in inspector to assign splash screen background image
     public Texture2D _splashScreenText;          //Creates slot in inspector to assign splash screen text
 
     private AudioSource _splashScreenAudio;      //Defines naming convention for audio source component
     public AudioClip _splashScreenMusic;        //Creates slot in inspector to assign splash screen music
 
     private float _splashScreenFadeValue;       //Defines fade value
     private float _splashScreenFadeSpeed = 0.15f;    //Defines fade speed
 
     private SplashScreenController _splashScreenController;
 
     private enum SplashScreenController
     {
         SplashScreenFadeIn = 0,
         SplashScreenFadeOut = 1
 
     }
 
     void Awake()
     {
         _splashScreenFadeValue = 0;  
     }
 
 
     // Start is called before the first frame update
     void Start()
     {
         Cursor.visible = false;
         Cursor.lockState = CursorLockMode.Locked;
 
         _splashScreenAudio = GetComponent<AudioSource>();
 
         _splashScreenAudio.volume = 0;
         _splashScreenAudio.clip = _splashScreenMusic;
         _splashScreenAudio.loop = true;
         _splashScreenAudio.Play();
 
         _splashScreenController = SplashScreen.SplashScreenController.SplashScreenFadeIn;
 
         StartCoroutine("SplashScreenManager");
 
     }
 
     // Update is called once per frame
     void Update()
     {
         
     }
     private IEnumerable SplashScreenManager()
     {
         while (true)
         {
             switch(_splashScreenController)
             {
                 case SplashScreenController.SplashScreenFadeIn:
                     SplashScreenFadeIn ();
                     break;
                 case SplashScreenController.SplashScreenFadeOut:
                     SplashScreenFadeOut ();
                     break;
             }
 
             yield return null;
         }
 
 
     }
 
     private void SplashScreenFadeIn()
         
     {
         Debug.Log("SplashScreenFadeIn");
 
         _splashScreenAudio.volume += _splashScreenFadeSpeed * Time.deltaTime;
         _splashScreenFadeValue += _splashScreenFadeSpeed * Time.deltaTime;
 
         if (_splashScreenFadeValue > 1)
             _splashScreenFadeValue = 1;
 
         if (_splashScreenFadeValue == 1)
             _splashScreenController = SplashScreen.SplashScreenController.SplashScreenFadeOut;
         
 
         
     }
 
     private void SplashScreenFadeOut()
     {
         Debug.Log("SplashScreenFadeOut");
 
         _splashScreenAudio.volume -= _splashScreenFadeSpeed * Time.deltaTime;
         _splashScreenFadeValue -= _splashScreenFadeSpeed * Time.deltaTime;
 
         if (_splashScreenFadeValue < 0)
             _splashScreenFadeValue = 0;
 
         if (_splashScreenFadeValue == 0)
             SceneManager.LoadScene("ControllerWarning");
             
 
 
 
     }
 
     private void OnGUI()
     {
         GUI.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), _splashScreenBackground);
 
         GUI.color = new Color (1, 1, 1, _)
 
         GUI.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), _splashScreenText);
     }
 
 
 
 }