Cool. So, Yesterday and today, I when through all the steps again, and re-pasted every ID, Key, and piece of information I could. None of it worked. I went to the API console and messed with the auth page a bit trying to find out how to add the preview domain to the authorized URLs, and then saved it all and went to bed. This morning, low and behold, the leaderboard is working. Now, I have no idea what I did to make it work, but it is working! YAY!
I still can't get the preview to work, but that's ok. At least I have the leaderboards working when exported to google play.
So, now I am back to the original purpose of this post, which is to ask a few questions about the specific functions of the google play plugin.
First, What is up with the saved games feature that I posted about toward the start of this thread?
Second, Is there a way to set a leaderboard to only ever keep one entry from any player? One of my leaderboards is the top win-rates, and I want every player to have one place on it. Is this possible? Or is there like a way to delete your last entry?
Third, can we get some more detailed instructions for how to add construct as a preview URL for google play leaderboards?