does not implement interface member

i am using unity 5.5 beta and i just got a plugin for google play services from here: GitHub - playgameservices/play-games-plugin-for-unity: Google Play Games plugin for Unity

and got an error saying

Assets/GooglePlayGames/ISocialPlatform/PlayGamesLocalUser.cs(27,18): error CS0535: GooglePlayGames.PlayGamesLocalUser' does not implement interface member UnityEngine.SocialPlatforms.ILocalUser.Authenticate(System.Action)’

here is the suggested answer by Kidel but i don’t know how to implement it !
[82102-playgameslocaluser.zip|82102]

please help.

PlayGamesLocalUser script is attached with this question

я нашел решение, заменить нужно пару файлов и заработало, как по маслу… правд проверял я на Unity3D 5.5 не бета версии. - но суть та же, после обновы Unity3D, google-play service перестала работать.

а ща все летает просто отлично)

did u manage to fix it?