iPhone Store Kit "Cannot connect to iTunes Store"

I was getting SKPaymentTransactionStateFailed error code 0 "Cannot connect to iTunes Store" and thanks to thomax for this answer my problem is solved. Turns out you MUST enter a build number under Targets->Summary.

I spent the last 24 hours resetting my phone, screwing with iTunes connect, and doing just about everything i could think of before i stumbled upon this solution.

I assume you've done the standard sanity checks: double-checking your code, confirming your product IDs, comparing your code to the In-App Purchase Programming Guide, etc.

This may be ridiculous, but -- if you're certain your code is correct -- do a hard reset (full wipe) of your iPod (Settings => General => Reset => Erase All Content and Settings). I puzzled over this exact problem for hours -- it turned out my code was correct and the hard reset was the solution.

I had been getting the same error but I had been prompted for my test user account. And also a popup saying "An unknown error has occurred". It turns out that when I created my test user account and signed out of the settings -> store I had decided to sign in with my test user account which had prompted me for a bunch of information including billing, which had broken my test user account. When I created a new test user account and only signed in when prompted to during the in app purchase testing, everything worked smoothly.