Google Games Plugin login not working ?

Hello everyone ,
i am using google games plugin in my game. When i tried to call the authenticate function (LOGIN) , nothing happens not even a login pop up shows . I did everything that was said in the document .The app is live on playstore with game services implemented and signed apk. But nothing happens not even login pop-up shows. Please help me that would be very grateful . Thank you

PlayGamesClientConfiguration config = new PlayGamesClientConfiguration.Builder()
.RequestEmail()
.Build();
PlayGamesPlatform.InitializeInstance(config);
PlayGamesPlatform.DebugLogEnabled = true;
PlayGamesPlatform.Activate();

Social.localUser.Authenticate((bool success) =>
{
if (success)
{
print(“Login”)
}

});

Share the logcat log to see whats going wrong.

Hi Sir thank for the reply . i solved this issue by doing some changes in the mainfest file . But now i am stuck in a problem. I am using appodeal and google games plugin in my game. When i start the game a toast message shows “Admob not found”

If you are using Admob, you may need to configure on Appodeal dashboard giving them the access to your Admob profile.

Yes i have synced my admob account with appodeal. Since i added google games plugin in my game , i am getting toast error at the start of the game that “Admob not found”. please check the screenshot for more detail. Thank you