Switching camera angles doesn't work, sticks on one menu.

So I'm attempting to make a menu that switches cameras when you click on the buttons. It works, but only one time. So, for example, if I click on help, then click the back button, it just sticks on the help menu.

 public var clicked : boolean = false;
 var CameraMenu : Camera;
 var CameraHelp : Camera;
 var CameraStart : Camera; //These are for transforming to the other menus/starting the game.
 
 public function OnMouseDown()
 {
     clicked = !clicked;
         CameraMenu.enabled = false;
         CameraHelp.enabled = true;
             CameraStart.enabled = false;
     GameObject.FindGameObjectWithTag("Help Menu");
 }