Cursor.LockState = CursorLockMode.Locked doasnt works.

i wanted to create a pause menu screen and make it when it is on the cursor lock mode is in none and when the menu is off the cursor is locked, but when i try to lock exiting from the menu it doasnt locks.

here is my code:

using UnityEngine; using System.Collections; using System.Text; using UnityEngine.UI;

namespace UnityStandardAssets.ImageEffects { public class PAUSEMENU : MonoBehaviour {

     public GameObject menu;

     public Slider sensitivity;
     public Text S_Value;

     void Start()
     {
         Cursor.visible = false;
         Cursor.lockState = CursorLockMode.Locked; //<- here works
     }

     void Update()
     {
         Debug.Log(Cursor.lockState);

         Blur effect1 = GetComponentInChildren<Blur>();
         Tonemapping effect2 = GetComponentInChildren<Tonemapping>();

         MouseLook camov = GetComponent<MouseLook>();
         camov.sensitivityX = sensitivity.value;
         camov.sensitivityY = sensitivity.value;

         S_Value.text = "" + sensitivity.value;

         if (Input.GetKeyDown(KeyCode.Escape))
         {
             if (Time.timeScale == 1)//pause ON
             {
                 Time.timeScale = 0;
                 menu.active = true;

                 Cursor.lockState = CursorLockMode.None;
                 Cursor.visible = true;

                 effect1.enabled = true;
                 effect2.enabled = true;

                 camov.active = false;
             }
             else if (Time.timeScale == 0)// pause OFF
             {
                 Time.timeScale = 1;
                 menu.active = false;

                 Cursor.lockState = CursorLockMode.Locked; //<-- but here no
                 Cursor.visible = false;

                 effect1.enabled = false;
                 effect2.enabled = false;

                 camov.active = true;
             }
         }
     }
 }

}