Problem implementing google oauth authentication

Hi,

I am trying to implement google oauth login for my unity game. Am currently doing the following stuff

   void Start()
     {
         PlayGamesClientConfiguration config = new PlayGamesClientConfiguration.Builder()
         .AddOauthScope("email")
         .AddOauthScope("profile")
         .AddOauthScope("https://www.googleapis.com/auth/games")
         .AddOauthScope("https://accounts.google.com/o/oauth2/auth")
         .Build();
 
         PlayGamesPlatform.InitializeInstance(config);
         // recommended for debugging:
         PlayGamesPlatform.DebugLogEnabled = true;
         // Activate the Google Play Games platform
         PlayGamesPlatform.Activate();
         //PlayGamesPlatform.Instance.Authenticate(GetData);
         Social.localUser.Authenticate(GetData);
     }

when a button is pressed

  public void OnButtonPress()
     {
         PlayGamesPlatform.Instance.GetServerAuthCode(AuthoResponse);
     }

 private void AuthoResponse(CommonStatusCodes result,string status)
     {
         Debug.Log("status of autho:"+result.ToString()+"\nStatus:"+status);
     }

the above code returns a internal error when "GetServerAuthCode" method is called. I have tried to get access token using "PlayGamesPlatform.Instance.GetAccessToken()" it doesn't return any data.

I searched for documentation, but there was not much related to unity. Can you please point me in the right direction.

Thank you.