Google Play Games Plugin Authenticating but failing to show leaderboard UI!

Hi everyone, I have successfully integrated the Google Play Games plugin, however, the leaderboard is not showing when it's called. I tried deploying and testing many builds ( 10+ and counting), but it can't seem to work.

This is my code:`

using UnityEngine;

using System.Collections;

using GooglePlayGames;

using UnityEngine.SocialPlatforms;

using GooglePlayGames.BasicApi;

public class ShowLeaderboard : MonoBehaviour {

 public void ShowLB()
 {
     Social.ShowLeaderboardUI ();
 }

} `