Toggling a game object between an active and inactive state

I have an application I'm developing for iOS. When an object is touched, it disappears, adds points to a score, and then respawns in a new location after 5 seconds. I'm having trouble with the object respawning, but the essential problem is in the abbreviated script I wrote below. Why doesn't this code re-activate the game object and what's the best way to toggle between active and inactive for iOS?

 function Start () {
 
     gameObject.active = false; 
     yield WaitForSeconds(5.0); // wait for 5 seconds        
     gameObject.active = true; 
     yield WaitForSeconds(5.0); // wait for 5 seconds 
     gameObject.active = false; 
     yield WaitForSeconds(5.0); // wait for 5 seconds        
     gameObject.active = true;
 
 }