I recently updated "The Creeps!" to add DLC level packs and started getting support emails about users being prompted to create a test account for the sandbox environment! After one email, I was convinced it was just a problem with pirated copies (I even thought my beta had been leaked for a while). But after getting more and more emails with people having the same problem I did some research and found this: http://help.boxcar.io/faqs/general/cant-use-in-app-purchase-this-is-not-a-test-user-account So if you add DLC to your game, expect to get support emails with this issue. But at least there's a fix for it! I thought you guys would like to know
Yeah, I never had the problem but that was because I took steps to solve it before it was even a problem for me. I honestly don't know what it is about app sync that makes DLC not work.