java.lang.ClassNotFoundException: com.google.android.gms.games.Games

I tried implementing Google Services in my game, I've done every setup including the SHA 1 key but am getting this error from logcat each time i try signing in:

 01-30 13:35:31.852 30868 30886 I Unity   : CloudOnce.Internal.Providers.GooglePlayGamesCloudProvider:Initialize(Boolean, Boolean, Boolean)
 01-30 13:35:31.852 30868 30886 I Unity   :
 01-30 13:35:31.859 30868 30886 E Unity   : AndroidJavaException: java.lang.ClassNotFoundException: com.google.android.gms.games.Games
 01-30 13:35:31.859 30868 30886 E Unity   : java.lang.ClassNotFoundException: com.google.android.gms.games.Games
 01-30 13:35:31.859 30868 30886 E Unity   :      at java.lang.Class.classForName(Native Method)
 01-30 13:35:31.859 30868 30886 E Unity   :      at java.lang.Class.forName(Class.java:453)
 01-30 13:35:31.859 30868 30886 E Unity   :      at com.unity3d.player.UnityPlayer.nativeRender(Native Method)
 01-30 13:35:31.859 30868 30886 E Unity   :      at com.unity3d.player.UnityPlayer.access$300(Unknown Source:0)
 01-30 13:35:31.859 30868 30886 E Unity   :      at com.unity3d.player.UnityPlayer$e$1.handleMessage(Unknown Source:95)
 01-30 13:35:31.859 30868 30886 E Unity   :      at android.os.Handler.dispatchMessage(Handler.java:102)
 01-30 13:35:31.859 30868 30886 E Unity   :      at android.os.Looper.loop(Looper.java:214)
 01-30 13:35:31.859 30868 30886 E Unity   :      at com.unity3d.player.UnityPlayer$e.run(Unknown Source:20)

Any help on this will be appreciated.