Google Play Game for Unity doesn't work

Hi!

I am trying to add Google Play Services for my android game, but i can't. I have installed all plugins and uploaded apk to Google Play.

Here is my code:

  using UnityEngine;
  using System.Collections;
  using GooglePlayGames;
  using UnityEngine.SocialPlatforms;
  
  
  public class GPG : MonoBehaviour {
  
  void Start()
  {
  PlayGamesPlatform.Activate ();
  }
  
  
  public void Awake ()
 {
     Social.localUser.Authenticate ((bool success) =>
     {
         if (success) {
             Debug.Log ("Login Sucess");
         } else {
             Application.Quit();
         }
     });
 }
  
      
      public void PostLeaderBoard () 
      {
          if (Social.localUser.authenticated) 
          {
         Social.ReportScore (5000, "MyLeaderboardID", (bool success) =>
         {
             if (success) {
                 LeaderBoard ();
             } else {
                 Application.Quit();
             }
         });
         } 
      }
  
  public void LeaderBoard () 
  {
     ((PlayGamesPlatform) Social.Active).ShowLeaderboardUI("MyLeaderboardID");
  }
  
  }

If I run my game on phone, then sign in box does't appear and if I call PostLeaderBoard (), my game does't close.

Hope someone can help.