Showing Google Play Game Leaderboard UI not working at all

Trying to figure out what went wrong with t$$anonymous$$s GPG plugin. I followed the instructions and understand the document in order to test run the login and show leaderboard UI via t$$anonymous$$s one. I did make the play games ac$$anonymous$$evements + leaderboard via Google Play developer account, do the setup, copy-paste source, and done. Testing the ads via adding Admob Unity package and GPG Unity package and it worked perfectly. I even update some plugins for Android (etc. .aar files, firebase-common, manifest) in order to maximize compatibility and efficiency so that I could build APK without any issues that interfering the build-up.

However, there is one issue: after I logged in and trying to tap the "show leaderboard UI" button along with the button event that asks if the user is authenticated and it will allow you to record your latest $$anonymous$$ghscore by updating it before showing the leaderboard UI. Here's how the code works:

First, at the Start() callback...

 PlayGamesClientConfiguration config = new PlayGamesClientConfiguration.Builder()
         .Build();

     PlayGamesPlatform.InitializeInstance(config);
     PlayGamesPlatform.DebugLogEnabled = true;
     PlayGamesPlatform.Activate();

Next, here's the login/logout process...

 public void LogInAccount() {
 // Show dialog.
 y = 0;
 dialogPanel.SetActive (true);
 dialogBackground.SetActive (true);

 // You can logout if you're logged in.
 if(Social.localUser.authenticated) {

     ((PlayGamesPlatform)Social.Active).SignOut ();

     y = 0;
     message.text = "Your account have been logged out.";
     logButtonLabel.text = "Log-in via Google";
     button.SetActive (true);
     confirmSound.Play();

     return;

 } 

 // Check for status.
 if (CheckNetwork.checkOnlineStatus ()) {
 
     Social.localUser.Authenticate ((bool success) => {

         if (success) {

             // LOG IN SUCCESS! (Check if the email is identified or not.)
             if((((PlayGamesLocalUser)Social.localUser).Email != null) || (((PlayGamesLocalUser)Social.localUser).Email != "")) {

                 y = 0;
                 message.text = "Login complete. However, email is not verified or unknown.";
                 logButtonLabel.text = "Log-out";
                 button.SetActive (true);
                 errorSound.Play();

             } else {

                 y = 0;
                 message.text = "Login complete!\nYour email:" + ((PlayGamesLocalUser)Social.localUser).Email;
                 logButtonLabel.text = "Log-out";
                 button.SetActive (true);
                 confirmSound.Play();

             }

         } else if (!success) {

             // LOG IN FAILED.
             if((((PlayGamesLocalUser)Social.localUser).Email != null) || (((PlayGamesLocalUser)Social.localUser).Email != "")) {

                 message.text = "Login failed. Please try again later.\nYour email: ? ? ?";

             } else {

                 message.text = "Login failed. Please try again later.\nYour email: " + ((PlayGamesLocalUser)Social.localUser).Email;

             }

             y = 0;
             button.SetActive (true);
             logButtonLabel.text = "Log-in via Google";
             errorSound.Play();

         }

     });

 } else {
 
     message.text = "Connection is lost. Please enable online.";
     button.SetActive (true);

 }

}

And then, the show leaderboard callback/button event.

     public void OpenLeaderboard() {
 
         // Show dialog.
         y = 0;
         dialogPanel.SetActive (true);
         dialogBackground.SetActive (true);
 
         // Check for status.
         if (Social.localUser.authenticated && CheckNetwork.checkOnlineStatus ()) {
 
             // Updating your $$anonymous$$ghscore...
             Social.ReportScore ((long)Score.GetScore (), 
                 Ac$$anonymous$$evementReference.leaderboard_best_intergalactic_chasers_top_score,
                 (bool success) => {
 
                     if(success) {
 
                         // LEADERBOARD APPEARED!
                         dialogPanel.SetActive (false);
                         dialogBackground.SetActive (false);
                         confirmSound.Play();
                         Social.ShowLeaderboardUI();
 //                        ((PlayGamesPlatform)Social.Active).ShowLeaderboardUI(Ac$$anonymous$$evementReference.leaderboard_best_intergalactic_chasers_top_score);
 
                     } else {
 
                         y = 0;
                         message.text = "Load failed. Please try again later.";
                         button.SetActive (true);
                         errorSound.Play();
 
                     }
 
                 });
 
         } else if (!Social.localUser.authenticated) {
 
             y = 0;
             confirmSound.Play();
             button.SetActive (true);
         
             if (!CheckNetwork.checkOnlineStatus ()) {
 
                 message.text = "Connection not available at a moment.";
 
             } else if (CheckNetwork.checkOnlineStatus ()) {
 
                 message.text = "You must login first in order to see the leaderboard.";
 
             }
 
         }
 
     }

At my first attempt, I do login (it shows the welcome sign sometimes) and tap the leaderboard button but not$$anonymous$$ng happens after 2 minutes. Second attempt, I do login-logout-login method and the GPG prompted me to select the Email address and the welcome username sign appeared on top. However, still...when I tapped the show leaderboard UI button and not$$anonymous$$ng happens after 3 minutes. I used t$$anonymous$$s reference to gain more ideas on effective showing the leaderboardc UI and checked for the code sample. Final attempt, and I assumed that leaderboard UI won't show up until I publish the Game Services I've created (it was set for testing mode before) and see if the leaderboard UI is working or not. Then after a day or two, used the same method from first second attempt and still got no luck.

The question is: how come the leaderboard UI still won't show-up during test mode and even after published the game services via Google play Services developer section? The same t$$anonymous$$ng happen in displaying in Ac$$anonymous$$evements UI. What was the cause that preventing the leaderboard UI from showing up even if I did it correctly on the setup? I doubt it's the internet connection issues or wifi signal. The issues probably is the long load on a very simple game services I've made. I only created only two leaderboards ($$anonymous$$ghscore and no. of s$$anonymous$$ps destroyed) and five ac$$anonymous$$evements on reac$$anonymous$$ng certain score and no. of s$$anonymous$$ps destroyed. Please help.

Also, aside from showing leaderboard UI issues, there is also an error that leaves the string value (actually, I'm retrieving with the email address selected) null or empty even if successfully logged in via Google account follow-up by the welcome username sign at the top of the screen.

UPDATE (As of 2:46 PM via P$$anonymous$$lippines, 7/5/2016): After I checked the bugs and offer some solution from S. Tarik Cetin, I checked on logcat about login. At first, I thought it's successful login. Then, I noticed t$$anonymous$$s:

 W/Unity   (32099): *** [Play Games Plugin DLL] 07/05/16 14:33:54 -07:00 ERROR: E
 xception launc$$anonymous$$ng token request: java.lang.ClassNotFoundException: com.google.g
 ames.bridge.TokenFragment
 W/Unity   (32099):
 W/Unity   (32099): (Filename: ./artifacts/generated/common/runtime/UnityEngineDe
 bugBindings.gen.cpp Line: 37)
 W/Unity   (32099):
 W/Unity   (32099): *** [Play Games Plugin DLL] 07/05/16 14:33:54 -07:00 ERROR: U
 nityEngine.AndroidJavaException: java.lang.ClassNotFoundException: com.google.ga
 mes.bridge.TokenFragment
 W/Unity   (32099): java.lang.ClassNotFoundException: com.google.games.bridge.Tok
 enFragment
 W/Unity   (32099):      at java.lang.Class.classForName(Native Method)
 W/Unity   (32099):      at java.lang.Class.forName(Class.java:217)
 W/Unity   (32099):      at java.lang.Class.forName(Class.java:172)
 W/Unity   (32099):      at com.unity3d.player.UnityPlayer.nativeRender(Native Me
 thod)
 W/Unity   (32099):      at com.unity3d.player.UnityPlayer.a(Unknown Source)
 W/Unity   (32099):      at com.unity3d.player.UnityPlayer$b.run(Unknown Source)
 W/Unity   (32099): Caused by: java.lang.NoClassDefFoundError: com/google/games/b
 ridge/TokenFragment
 W/Unity   (32099):      ... 6 more
 W/Unity   (32099): Caused by: java.lang.ClassNotFoundException: com.google.games
 .bridge.TokenFragment
 W/Unity   (32099):      at dalvik.system.BaseDexClassLoader.findClass(BaseDexCla
 ssLoader.java:61)
 W/Unity   (32099):      at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
 
 W/Unity   (32099):      at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
 
 W/Unity   (32099):      ... 6 more
 W/Unity   (32099):   at UnityEngine.AndroidJNISafe.CheckException () [0x00000] i
 n <filename unknown>:0
 W/Unity   (32099):   at UnityEn

Also, I encountered the status form my logcat when I did sign-in and out once.

 W/Unity   (32099):   at UnityEn
 I/Unity   (32099):  [Play Games Plugin DLL] 07/05/16 14:38:07 -07:00 DEBUG: Star
 ting Auth Transition. Op: SIGN_OUT status: ERROR_NOT_AUTHORIZED
 I/Unity   (32099):
 I/Unity   (32099): (Filename: ./artifacts/generated/common/runtime/UnityEngineDe
 bugBindings.gen.cpp Line: 37)
 I/Unity   (32099):

Finally, here's the issue found during attempt on opening leaderboard UI directly.

 W/Unity   (32099): *** [Play Games Plugin DLL] 07/05/16 14:40:31 -07:00 ERROR: U
 nityEngine.AndroidJavaException: java.lang.ClassNotFoundException: com.google.ga
 mes.bridge.NativeBridgeActivity
 W/Unity   (32099): java.lang.ClassNotFoundException: com.google.games.bridge.Nat
 iveBridgeActivity
 W/Unity   (32099):      at java.lang.Class.classForName(Native Method)
 W/Unity   (32099):      at java.lang.Class.forName(Class.java:217)
 W/Unity   (32099):      at java.lang.Class.forName(Class.java:172)
 W/Unity   (32099):      at com.unity3d.player.UnityPlayer.nativeRender(Native Me
 thod)
 W/Unity   (32099):      at com.unity3d.player.UnityPlayer.a(Unknown Source)
 W/Unity   (32099):      at com.unity3d.player.UnityPlayer$b.run(Unknown Source)
 W/Unity   (32099): Caused by: java.lang.NoClassDefFoundError: com/google/games/b
 ridge/NativeBridgeActivity
 W/Unity   (32099):      ... 6 more
 W/Unity   (32099): Caused by: java.lang.ClassNotFoundException: com.google.games
 .bridge.NativeBridgeActivity
 W/Unity   (32099):      at dalvik.system.BaseDexClassLoader.findClass(BaseDexCla
 ssLoader.java:61)
 W/Unity   (32099):      at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
 
 W/Unity   (32099):      at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
 
 W/Unity   (32099):      ... 6 more
 W/Unity   (32099):   at UnityEngine.AndroidJNISafe.CheckException () [0x00000] i
 n <filen

UPDATE (As of 5:29 PM via P$$anonymous$$lippines, 7/5/2016): I made a mistake about checking if the email is empty or not. I made a reading wrong. Though, email address value still has issue and it should return with identified ones in string value and leaving with a blank when it reads not empty.

 // LOG IN SUCCESS! (Check if the email is identified or not.)
 if((((PlayGamesLocalUser)Social.localUser).Email != null) || (((PlayGamesLocalUser)Social.localUser).Email != "")) {
 
     y = 0;
     message.text = "Login complete!\nYour email:" + ((PlayGamesLocalUser)Social.localUser).Email;
     logButtonLabel.text = "Log-out";
     button.SetActive (true);
     confirmSound.Play();
 
 } else {
 
     y = 0;
     message.text = "Login complete. However, email is not verified or unknown.";
     logButtonLabel.text = "Log-out";
     button.SetActive (true);
     errorSound.Play();
 
 }