OnGui Button not displaying

Hi guys! I'm working through the book "Learning C# by Developing Games with Unity" and have come into some trouble with my state machine. I'm supposed to have a button showing that says Press to play, the game will be paused and then when you press the button the game unpauses.

Here is the code:

StateManager script:

 using UnityEngine;
 using Assets.Code.States;
 using Assets.Code.Interfaces;
 public class StateManager : MonoBehaviour 
 {
     private IStateBase activeState;
 
     // Use this for initialization
     void Start () 
     {
         activeState = new BeginState(this);
     }
 
     // Update is called once per frame
     public void Update () 
     {
         if (activeState != null)
             activeState.StateUpdate();
     }
     public void onGUI()
     {
         if(activeState != null)
             activeState.ShowIt();
     }
     public void SwitchState(IStateBase newState)
     {
         activeState = newState;
     }
 }

Here is the BeginState script:

 using UnityEngine;
 using Assets.Code.Interfaces;
 
 namespace Assets.Code.States
 {
     public class BeginState : IStateBase
     {
         private StateManager manager;
 
         public BeginState (StateManager managerRef)    //Constructor
         {
             manager = managerRef;
             Debug.Log ("Construction BeginState");
         }
 
         public void StateUpdate()
         {
             if (Input.GetKeyUp (KeyCode.Space)) 
             {
                 manager.SwitchState (new PlayState (manager));
             }
         }
 
         public void ShowIt ()
         { 
             if (GUI.Button (new Rect (10, 10, 150, 100), "Press to Play")) 
             {      
                 Time.timeScale = 1;
                 manager.SwitchState (new BeginState (manager));  
             }
         }
     }
 }

Here is the IStateBase script

 namespace Assets.Code.Interfaces
 {
     public interface IStateBase
     {
         void StateUpdate();
         void ShowIt();
     }
 }