Load Scene Unity by Application.LoadLevelAsync

I use the function Application.LoadLevelAsync (s); in the game but it just stops at 89%. I have read some posts on the forum but did not solve the problem. Help me fix that. my code below:

 public void LoadScenes (string s)
 {
     if (!quit) {
         SoundController.PlaySound (soundGame.ButtomClick);
         progressBars.gameObject.SetActive (true);
         background.SetActive (true);
         text.gameObject.SetActive (true);
         async = Application.LoadLevelAsync (s); 
         async.allowSceneActivation = false;
         StartCoroutine (DisplayLoadingScreen ());
     }
 }
 IEnumerator DisplayLoadingScreen ()
 {
     while (!async.isDone) {
         loadProgress = (int)(async.progress * 100);
         text.text = "Loading Progress " + loadProgress + "%";
         progressBars.size = loadProgress;
         yield return null;
     }
     if (async.isDone) {
         Debug.Log ("Loading complete");
         async.allowSceneActivation = true;
     }
 }