Naomi,
I just implemented GPGS yesterday and ran into the same problem but was pretty simple to fix (at least in my case).
You don’t even need to publish an alpha build of your app or publish your GPGS data to get it working, just have your app ready to publish and by that I mean add some dummy store data, and upload your apk from that point when you run through the wizard and put in the product id of your app it should pick up the rest of the info for you and link the two.
First things first is to go to the developer console (API) (https://code.google.com/apis/console) and make sure you have Google Play Game Services and Google Play Game Management turned on which seems fairly obvious lol
I just created a test for GPGS and wrote down the steps I took and everything worked with zero issues.
1: Create a new application in Google Developer (just store listing not APK) – (just add dummy info for desc and hit save)
2: Click on services and APIs and grab the license key and put it in the config.lua file (application->license section)
3: Compile my APK and upload it (don’t publish just save)
4: Click on Game Services and Add New Game
5: Use “I don’t use any google apis in my game yet” and fill in the name and category.
6: Follow the wizard and clicking next etc.
7: Make sure you put in the product id (com.yourapp.game) of your build when asked.
8: IGNORE the SHA stuff it will auto-add it for you (at least that has been my experience) and continue.
9: Take the number it gives you (which should say something like this is the only number you need)
10: Add that number to your build.settings file for googlePlayGamesAppId in the android section.
11: Add 5 achievements and 1 leaderboard.
12: In testing (Game Services->Game Item->Testing) add the gmail account of the “logged in” account of your android device (doesn’t need to be in alpha or beta).
12: add the codes to the lua note: I add to google first so i can use the same ID on apple.
local leaderID = “CgkI7Lva9bAbEAIQBg”
local achievementID = {
{key = “A1”, id = “CgkI7Lva9bAbEAIQAQ”},
{key = “A2”, id = “CgkI7Lva9bAbEAIQAg”},
{key = “A3”, id = “CgkI7Lva9bAbEAIQAw”},
{key = “A4”, id = “CgkI7Lva9bAbEAIQBA”},
{key = “A5”, id = “CgkI7Lva9bAbEAIQBQ”},
}
13: Add this (USE::userInitiated = true) NOT FALSE -> using false made everything fail on my side (just a side note))
gameNetwork = require “gameNetwork”
gameNetwork.init(“google”)
gameNetwork.request(“login”,{userInitiated = true})
14: Test with
–Show Leaderboards
timer.peformWithDelay(1000, function()
gameNetwork.show(“leaderboards”)
end, 1)
–Show Achievements
timer.peformWithDelay(1000, function()
gameNetwork.show(“achievements”)
end, 1)
–Unlock Achievement
timer.peformWithDelay(1000, function()
gameNetwork.request(“unlockAchievement”, {achievement = {identifier = achievementID[“A1”].id}})
end, 1)
If you use USB debugging on your android like me.
14: plug in your device to your computer
15: Rebuild and push to your device with adb -d install -r “C:\path\mygame.apk”
16: run adb logcat
17: run your game and see what is going on 
18: everything works fine
Not sure if that helps but those are the steps I just did on a brand new project in corona.
