Leaderboards and achievements not working -- Google Play Services

Hello! I've researched for over two days now, and I simply can't get this to work. I'm using the latest version of Unity, imported Play Store plugins, and the following code to display my leaderboards.

  using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.SocialPlatforms;
 using GooglePlayGames;
 
 public class GoogleHelper : MonoBehaviour {
 
     private bool connected = false;
     private Text text;
 
     void Start(){
         //PlayGamesPlatform.Activate();
         text = GetComponent<Text>();
         signIn();
     }
 
     private void signIn(){
         Social.localUser.Authenticate((bool success) => {
             connected = success;
         });
         text.text = connected + "<---";
     }
 
     public void toAchievements(){
         if (Social.localUser.authenticated){
             Social.ShowAchievementsUI();
         }
     }
 
     public void toLeaderboard(){
         if (Social.localUser.authenticated){
             Social.Active.ShowLeaderboardUI();
         }
     }
 
 }

I'm using the Text class to see if I'm connected, and both, in the editor, and the emulator - the outcome is "true."

To test, I'm using BlueStacks with a google account that is registered as a tester, but whenever I click on the button, I get a message "ShowLeaderboardUI not implemented"

The bundle i got: https://github.com/playgameservices/play-games-plugin-for-unity

Thanks for your help in advance!