Make sure you have the money to at least buy the gralat pack, but i suggest if you access your account through facebook I would use paypal to buy the gralats or some other method.  

If it says 'failed to purchase' that means you are low on credit.

If it says 'Sandbox error' Its because of your jailbreak IF your device is jailbroke.  

Email the iTunes receipt to [email protected] and be patient for him to add the gralats manually.  

I have money, I've renewed it during the time it hasn't worked as well. I don't get a receipt because I never actually purchase it. And I don't access my account through facebook so... :/

Thanks anyways.