Time.timescale=0 not working when the timeleft "countdown" reduce to 0

the game should stop if the timeleft=0 on update. Can someone tell me why and fix the scripts ThankYOu

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

public class FailedDialoue : MonoBehaviour { [SerializeField] private float timeLeft; [SerializeField] private Text text;

 [SerializeField]
 private int levelToLoad;

 [SerializeField]
 private GameObject dBox;
 [SerializeField]
 private Text dText;

 public bool dialogActive;

 public string[] dialogLines;
 public int currentLine;

 // Use this for initialization
 void Start()
 {

 }

 // Update is called once per frame
 void Update()
 {
     timeLeft -= Time.deltaTime;
     text.text = "Time Left:" + Mathf.Round(timeLeft);
     if (timeLeft < 0)
     {
         Time.timeScale = 0.0f;
         dBox.SetActive(true);
         dialogActive = true;
     }
     if (dialogActive && Input.GetKeyDown(KeyCode.Space))
     {
         //dBox.SetActive (false);
         //dialogActive = false;

         currentLine++;
     }
     if (currentLine >= dialogLines.Length)
     {
         dBox.SetActive(false);
         dialogActive = false;
         SceneManager.LoadScene(levelToLoad);


         currentLine = 0;
     }
     dText.text = dialogLines[currentLine];
 }

}