Sprite change doesn't work in built game.

I want to change the SpriteRenderer sprite to another one by pressing a GUI Button. In the editor, it works perfectly fine, with no problems. But when I build it for android or W.P, it doesn't work at all. The sprite remains the default one.

What happens in the editor: https://gyazo.com/88b8cf867d94932802bf9296d6fce0e6

What happens in built version(android): https://gyazo.com/9988c6a664c92c4b5703b7b8864990aa

Here is my script: using UnityEngine; using System.Collections;

 public class Shop : MonoBehaviour {
 
     int catPrice = 10;
     public Sprite defaultSprite;
     public Sprite catSprite;
     public GameObject Player;
     int moneyz;
     public bool hasBeenPressed;
     public SpriteRenderer spriteRenderer; 
     
     void Start () 
     {
         moneyz = PlayerPrefs.GetInt("Score");
         spriteRenderer = Player.GetComponent<SpriteRenderer>();
 
         int state = PlayerPrefs.GetInt("hasBeenPressed", 0);
         
         if (state == 1)
             hasBeenPressed = true;
         else
             hasBeenPressed = false;
     }
 
     public bool IsCatBought()
     {
         return hasBeenPressed;
     }
 
 
     void OnGUI()
     {
 
         if(!hasBeenPressed)
         {
             if(GUI.Button (new Rect(Screen.width / 2 - 30, 50, 90, 30), "Buy Cat Player."))
             {
                 if(PlayerPrefs.GetInt("Score", moneyz) < 10)
                 {
                     GUI.Label (new Rect(Screen.width / 2 - 40, 250, 100, 30), "Not enought moneyz");
                 }
                 else
                 {
                     PlayerPrefs.SetInt("Score", moneyz - catPrice);
                     Player.GetComponent<SpriteRenderer> ().sprite = Resources.Load("Player_Cat", typeof(Sprite)) as Sprite;
                     hasBeenPressed = true;
                     PlayerPrefs.SetInt("hasBeenPressed", 1);
                 }
             }
         }
 
         if(PlayerPrefs.GetInt("hasBeenPressed") == 1)
         {
             if(GUI.Button (new Rect(Screen.width / 2 - 30, 250, 90, 30), "Cat Player."))
             {
                 Player.GetComponent<SpriteRenderer> ().sprite = Resources.Load("Player_Cat", typeof(Sprite)) as Sprite;
             }
         }
 
         if(GUI.Button (new Rect(Screen.width / 2 - 40, 100, 100, 30), "Game"))
         {
             Application.LoadLevel(1);
         }
 
         if(GUI.Button (new Rect(Screen.width / 2 - 40, 150, 100, 30), "Back to Menu"))
         {
             Application.LoadLevel(0);
         }
 
         if(GUI.Button (new Rect(Screen.width / 2 - 40, 200, 100, 30), "Default Player."))
         {
             Player.GetComponent<SpriteRenderer> ().sprite = Resources.Load("Player_Normal", typeof(Sprite)) as Sprite;
         }
     }
 }

Also, I have used multiple ways to change the sprite but none of them worked.