Unity and Facebook SDK managing Score System

Hello!

I've been reading allot about this and there is very few information on this subject.

I am having trouble managing unity and facebook sdk with the score system.

So, I might be making some mistakes and I hope someone can help me through them.

So, when I open my game, I can either already be connected, or need to press the conenct button.

And this is the code I have so far.

The problem here is that I get an error when trying to POST a score = to 0.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using Facebook.MiniJSON;
 
 public class FacebookInit : MonoBehaviour {
 
     // Use this for initialization
     void Start () {
         FB.Init(OnInitComplete);
     }
 
     private void OnInitComplete()
     {
         if (FB.IsLoggedIn)
         {
             FB.API("/"+FB.UserId+"/scores", Facebook.HttpMethod.GET, retrieveScore);
             gameObject.SetActive(false);
         }
         else {
             gameObject.GetComponent<UILabel>().text = "Connect With Facebook!";
         }
     }
 
     void retrieveScore(FBResult result)
     {
         Dictionary<string, object> playerScore = Json.Deserialize(result.Text) as Dictionary<string, object>;
 
         object score;
         if (playerScore.TryGetValue("score", out score))
         {
             Debug.Log(score);
         }
         else
         {
             // Player has no score registered, so lets make it 0? Is this right?
             var wwwForm = new WWWForm();
             wwwForm.AddField("score", "0");
             FB.API("/" + FB.UserId + "/scores", Facebook.HttpMethod.POST, Callback, wwwForm);
         }
     }
 
     void Callback(FBResult result)
     {
         Debug.Log(result.Error);
     }
 
     public void CallFBLogin()
     {
         FB.Login("email,publish_actions", LoginCallback);
     }
 
     void LoginCallback(FBResult result)
     {
         if (result.Error != null){
             
             Debug.Log("Error Response:\n" + result.Error);
         }
         else if (!FB.IsLoggedIn)
         {
             Debug.Log("Login cancelled by Player");
         }
         else
         {
             Debug.Log("Login was successful!");
             FB.API("/" + FB.UserId + "/scores", Facebook.HttpMethod.GET, retrieveScore);
             gameObject.SetActive(false);
             
         }
     }
 }