Google Play Services Unity Plugin not Show Leaderboard

I am building a game for Android with Unity 5, and I have imported this: https://github.com/playgameservices/play-games-plugin-for-unity

and I followed this tutorial : https://www.youtube.com/watch?v=XmHXl-UFTqM

When I try to post or show leaderbord it does not show anything not even show any error. sign-in and out are working properly.Please any help or refrence :)

Code :

 using UnityEngine;
 using System.Collections;
 using GooglePlayGames;
 using UnityEngine.SocialPlatforms;
 
 public class LeaderBord : MonoBehaviour
 {
 
 
     string LeaderbordId = "CgkIxMxxxxxxxxxxxxxx"; 
 
     void Start ()
     {   
         PlayGamesPlatform.Activate ();
     
     }
      
 
     public void LogIn ()
     {
         Social.localUser.Authenticate ((bool success) =>
         {
             if (success) {
                 Debug.Log ("Login Sucess");
             } else {
                 Debug.Log ("Login failed");
             }
         });
     }
     
     public void LogOut ()
     {
         PlayGamesPlatform.Instance.SignOut ();
     }
 
     public void Post ()
     {
 
         if (Social.localUser.authenticated) {
             Social.ReportScore (5000, LeaderbordId, (bool success) =>
             {
                 if (success) {
                     ((PlayGamesPlatform)Social.Active).ShowLeaderboardUI (LeaderbordId);
                 } else {
                     Debug.Log ("Add Score Fail");
                 }
             });
         } 
     }
 
     public void ShowLeader ()
     {
         
         Social.ShowLeaderboardUI ();
     }         
 }