It's not an issue with the order of events. The sign-in basically fails. As a test I placed an -> on auto-sign in failed-sign-in event on the title page of my game and it is a continuously repeating instance of how you describe it: a dimming of the screen and the notification bar coming visible but nothing happening. Thus, it has to do with the setup of the google play plugin not the order of events.
Well, I got the auto-sign in to work! It loads the sign in screen with my avatar and confirms sign in like other games.
I left my order of events as they are in my previous post above. I have App ID and Game ID and Client ID entered, so not sure if that makes a difference having all 3 entered. And I also signed the APK with both V1 and V2 this time, so not sure if that made the difference.
I now have two remaining issues...
1- Loading the player's best high score and saving as global variable to set in text field. It's always stuck at 0.
2- And Display Leaderboards. When you click the icon to show leaderboard, a screen loads but the load circle just goes around and around.
Still testing. So I'll report back if I get these to work.