IAP - What am I missing?

OK, so I have tried to implement unity's IAP but I am... stuck.

I am only looking at android at present. I have signed up and created an app with Google Play.

I have tried following multiple guides, and here is what I am left with essentially in the project at this point. I enabled unity ads from the services window, and imported all of the stuff from there to the Plugins folder.

I have taken the "Purchaser" script from here: https://unity3d.com/learn/tutorials/topics/analytics/integrating-unity-iap-your-game and modified it to my own needs. I only have 1 product, which is a non consumable. I hooked it up to check this properly etc. In editor, it works as expected.

I submitted the APK to google play on my alpha testing platform, but the buy button does nothing once its uploaded there and I update on device. (I definitely have the right version).

The product I have was also created as an item for the app on Google play. Its identifier follows the pattern: "com.companyname.appname.productname" Then, in the purchaser script I set the Consumable Item name as such:

 public static string kProductIDNonConsumable = "com.companyname.appname.productname";

This is the product I am buying when I press the buy button, and the product I check for in ProcessPurchase().

So... Any ideas why it functions in editor etc, but when I build it and put it on google play it does nothing?