02 Setting up Games Services in Google Play Developer Console - myflashlab/GameServices-ANE GitHub Wiki

For your game to be able to connect to Google servers, you need a client ID and for this reason you need to register your package name into Google Play Console. NOTE: If you don't have experience in retrieving the fingerprints from .p12 certificates, you might find this step a bit confusing. But take your time and study this page here and Google will tell you how to setup the Game Services in your Google Play Console.

NOTICE you surely know this, so this is just a reminder... :) Android will add air. to the beginning of your Air package name. In other words, if your package name is com.site.myapp, your Android package name which you must register in Google Play Console is air.com.site.myapp. This is NOT true for the iOS setup though. On the iOS side, your bundle name will still be com.site.myapp