Mouse cursor doesn't lock Unity 5

Recently I have ran into a problem where I need to lock my mouse cursor but it doesn't lock. I have tried almost everything but the cursor just doesn't want to lock. Any ideas on how to lock it ?

My version of Unity is 5.1.1f1

Here is my code:

 public bool locked = false;
     
     void Update () 
     {
         if (Input.GetKeyDown(KeyCode.Escape))
         {
             locked = !locked;
         }
 
         if (locked)
         {
             Cursor.lockState = CursorLockMode.Locked;
             Cursor.visible = false;
         }
         else
         {
             
             Cursor.lockState = CursorLockMode.None;
             Cursor.visible = true;
         }
     }