There is a problem with my in-app purchase.

Quick fix: have you tried refreshing? (Sometimes it takes a few seconds for the new purchase to kick in, so closing and re-opening the app, or restarting your device, resolves most problems.)  

If this didn’t work, you can submit a report by using this form and picking the "Type of Issue" as "Purchase issue." In order for us to help you faster, please explain your issue in detail and include screenshots of your order confirmation or receipt.