Why Google Play Services doesn't work

I have a problem with the plugin Google Play Services, I installed this (https://github.com/playgameservices/play-games-plugin-for-unity) plugin and what happens to me is that i can't sign in well. When I go into the game and i log in i did not get the "banner" above with my user saying that I have logged in. And if after i press the buttons of ranking or medals asks me to log in again. After loggin it do not charge medals or rankings window it spends 2 seconds loading and returns to the game .... What I have to do to it work?

GPGS startup script: http: //pastebin.com/rVmzACxi

Script button: http://pastebin.com/7sr5n6cg