cursor not locking to the middle of the screen.,First person problem with the camera

Whenever I play the game I'm making, I always have to click first because the cursor is not locked until i click. Here is the code that is attached to my camera:

  public Transform player;
     public float mousesens = 10;
     private float x = 0;
     private float y = 0;
     
     // Start is called before the first frame update
     void Start()
     {
         Cursor.lockState = CursorLockMode.Locked;
     }
 
     // Update is called once per frame
     void Update()
     {
         x += -Input.GetAxis("Mouse Y") * mousesens;
         y += Input.GetAxis("Mouse X") * mousesens;
 
         x = Mathf.Clamp(x, -90, 90);
 
         transform.localRotation = Quaternion.Euler(x, 0, 0);
         player.transform.localRotation= Quaternion.Euler(0, y, 0);
     }

Is there anything wrong? my unity version is 2020.2.7f1 and I am using visual studio as my script editor.

thank you very much in advance