Mobile Buttons not working?

Hi,

This is the script attacted to my Sprite Button to Move Left:

 #pragma strict
 
 var Button : Sprite;
 var Button_Down : Sprite;
 var player : GameObject;
 
 function Start ()
 {
     player = GameObject.Find("player");
 }
 
 function OnMouseEnter()
 {
     GetComponent(SpriteRenderer).sprite = Button_Down;
 }
 
 function OnMouseExit()
 {
     GetComponent(SpriteRenderer).sprite = Button;
 }
 
 function OnMouseDown()
 {
     player.GetComponent(playerScript).MoveLeft();
 }

And this my playerScript (I wanted to be able to control with WASD - keycodes, and the buttons, I can control with keys, but the sprite buttons don't do anything..)

 #pragma strict
 
 var moveUp : KeyCode;
 var moveDown : KeyCode;
 var moveLeft : KeyCode;
 var moveRight : KeyCode;
 
 var GameManager : GameObject;
 
 var speed : float = 10;
 var stepSize : float = 1.6;
 
 function Start ()
 {
     GameManager = GameObject.Find("_GM");
 }
 
 function MoveUp ()
 {
     transform.Translate(0, stepSize, 0);
     GameManager.GetComponent.<gameManagerScript>().currentSteps += 1;
 }
 
 function MoveDown ()
 {
     GameManager.GetComponent.<gameManagerScript>().currentSteps += 1;
     transform.Translate(0, -stepSize, 0);
 }
 
 function MoveLeft ()
 {
     GameManager.GetComponent.<gameManagerScript>().currentSteps += 1;
     transform.Translate(-stepSize, 0, 0);
 }
 
 function MoveRight ()
 {
     transform.Translate(stepSize, 0, 0);
     GameManager.GetComponent.<gameManagerScript>().currentSteps += 1;
 }
 
 function Update()
 {
     // moving up
     if(Input.GetKeyDown(moveUp))
     {
         MoveUp();
     }
     // moving down
     else if(Input.GetKeyDown(moveDown))
     {
         MoveDown();
     }
     
     // moving left
     else if(Input.GetKeyDown(moveLeft))
     {
         MoveLeft();
     }
     
     // moving right
     else if(Input.GetKeyDown(moveRight))
     {
         MoveRight();
     }
 
     // stand still
     else 
     {
         GetComponent.<Rigidbody2D>().velocity.y = 0;
     }
 }

But the button IS not working. Yes I have added an 2D box collider with 'Is Trigger' enabled.

Any help would be appreciated!