Recently i was having multiple issues with google play games plugin integration in Unity. It was not working at all. After spending the couple of hours in it, i was able to fix the issue. This is a note to myself as well for others who are having trouble with the integration.
I was using Admob plugin along with Google Play Games plugin. In the process of fixing the error i got different kinds of error. Some error was due to the import while some was due to the Authentication issues from the play game service. I will discuss about these both.