renderer cannot enabled ..

what wrong with this script ??? at the beginning, mesh successfully enabled, but when mesh renderer not active and i am want to enable it again but that cannot active more, what's wrong?

sorry my bad english and thanks you

that my script : Can you fix it?

 public var isMeshOn :boolean ;
 
 function Start()
 {
 
     isMeshOn = true;
 }
     
 function Update () {
     if(Input.GetKeyDown(KeyCode.F))
     {
         if(isMeshOn)
             isMeshOn = false;
         else 
             isMeshtOn = true;
     }
         
     if(isMeshOn){
         gameObject.renderer.enabled = true;
     }
     else{
         gameObject.renderer.enabled = false;
     }
 }