Why does not this script work

using System.Collections.Generic;
using UnityEngine;

public class camMouseLook : MonoBehaviour {

	Vector2 mouselook;
	Vector2 SmoothV;
	public float sensitivity = 5.0f;
	public float smoothing = 2.0f;

	GameObject character;


	public GameObject backtogame;





	// Use this for initialization
	void Start () {
		character = this.transform.parent.gameObject;
	
	
	}
	
	// Update is called once per frame
	void Update () {
		var md = new Vector2 (Input.GetAxisRaw ("Mouse X"), Input.GetAxisRaw ("Mouse Y"));

		md = Vector2.Scale (md, new Vector2 (sensitivity * smoothing, sensitivity * smoothing));
		SmoothV.x = Mathf.Lerp (SmoothV.x, md.x, 1f / smoothing);
		SmoothV.y = Mathf.Lerp (SmoothV.y, md.y, 1f / smoothing);
		mouselook += SmoothV;

		transform.localRotation = Quaternion.AngleAxis (-mouselook.y, Vector3.right);
		character.transform.localRotation = Quaternion.AngleAxis (mouselook.x, character.transform.up);

		if (Input.GetKeyDown ("escape"))
			sensitivity = 0f;

			

		
		
	}

	public void Disable()
	{
		sensitivity = 5f;
		backtogame.SetActive (false);
		Cursor.lockState = CursorLockMode.Locked;

	}

}

So when i click the button that gets me back to the game i cant move the mouse. Why? Sensitivity is still 0 why?

Because You Didn’t Set It Back To The Default Value, You Wrote:

if (Input.GetKeyDown ("escape"))
             sensitivity = 0f;

And There Isn’t Something To Return It Back To “5f”, I Assume You Want To Stop The Mouse Look From Working When You Press “Escape” And Start Again When You Press “Escape” Again, So Here Is A Simple Solution:

private bool escape = false;
	void Update ()
	{
		if (Input.GetKeyDown ("escape") && !escape)
		{
			Debug.Log("Pressed Escape, So Sensitivity Is 0");
			sensitivity = 0f;
			escape = true;
		}
		else if (Input.GetKeyDown ("escape") && escape)
		{
			Debug.Log("Pressed Escape, So Sensitivity Is 5");
			sensitivity = 5f;
			escape = false;
		}
	}

Hope It Helps.

if (Input.GetKeyDown (“escape”) && !escape)
{
Debug.Log(“Pressed Escape, So Sensitivity Is 0”);
sensitivity = 0f;
escape = true;
Cursor.lockState = CursorLockMode.None;
backtogame.SetActive (false);
}

			else if (Input.GetKeyDown ("escape") && escape)
			{
				Debug.Log("Pressed Escape, So Sensitivity Is 5");
				sensitivity = 5f;
				escape = false;
				backtogame.SetActive(false);
				Cursor.lockState = CursorLockMode.Locked;
			}
		}

Why does not the canvas come up?? What type of variabel should i use?
And it only work one way