Script not actioned

I have got a class doing the following example login script

I have 10 out of 11 students with a working product from the following code. I have tried a new project, tried restarting the machine even. The one and only script attached to an empty game object does nothing. I put a debug.log in, and it doesn't run. I put the same debug.log in another persons script, same script, and it does work.

version 5.4.2

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class LoginMenu : MonoBehaviour {
5.  
6.     string loginURL = "http://127.0.0.1/login.php";
7.     string username = "";
8.     string password = "";
9.     string label = "";
10.    
11.     void OnGUI() {
12.         GUI.Window (0, new Rect (Screen.width / 4, Screen.height / 4, Screen.width / 2, Screen.height / 2 - 70), LoginWindow, "Login");
13.     }
14.    
15.     void LoginWindow(int windowID) {
16.         GUI.Label (new Rect (140, 40, 130, 100), "~~~~Username~~~~");
17.         username = GUI.TextField(new Rect(25, 60, 375, 30), username);
18.         GUI.Label (new Rect (140, 92, 130, 100), "~~~~~Password~~~~");
19.         password = GUI.PasswordField (new Rect (25, 115, 375, 30), password, '*');
20.         GUI.Button (new Rect (25, 160, 375, 50), "Login");
21.         GUI.Label (new Rect(55, 222, 250, 100), label);
22.     }
23. }