Collider Button don t work on Mobile Device

I have a problem with a collider button : when i use the button on PC it s work fine but when i use it on mobile device the script is not working (but the collider is making a fade effect)

Here is the "Start Game" script

 #pragma strict
 
 function OnMouseDown(){
     GameObject.FindWithTag("MainCamera").GetComponent(orbit).mainMenu = false;    
     for (var child : Transform in GameObject.Find("logo").transform) {
         child.gameObject.active = false;    
     }
     var enemy:GameObject[] = GameObject.FindGameObjectsWithTag("enemy");
     for (var child3 : GameObject in enemy) {
         Destroy(child3);
     }
     
     for (var child : Transform in GameObject.Find("menu_main").transform) {
         child.gameObject.active = false;    
     }    
     
     var num:GameObject[] = GameObject.FindGameObjectsWithTag("num");
     for (var child2 : GameObject in num) {
         Destroy(child2);
     }
     
     for (var child : Transform in GameObject.Find("menu_end").transform) {
         child.gameObject.active = false;    
     }    
     
     for (var child : Transform in GameObject.Find("healthbar").transform) {
         child.gameObject.active = true;    
     }    
     GameObject.Find("_Game").GetComponent(game).score = 0;    
 }
 

How I should modify to work on mobile ? (btw sorry for bad grammar)