I am testing in-app purchase functionality for my app.
The app is in alpha slot, product is active but I get errors saying "item not available" or similar when I test the functionality with release apk on real device (with gmail account in "license test response" list).
I see that the app is in draft state, is it the cause? I know draft state is not good for testing IAB but I followed the instructions about the alpha slot so I think I made no mistake.
I had the same problem, actually got here in search for a solution.
The reason was because the app was in "Draft" status due to some details in the configuration missing, especially the screenshots.
At the top right side of the page of the settings for the APK it must show Published, otherwise if it shows "Draft" it will give an option to see what's missing to publish.