With orders being sent to over 80 countries in the world, it is possible that from time to time you have a customer checkout from a country that you do not have a matching shipping rate from. When this happens, the customer cannot check out, however, we will notify you so that you have the opportunity to create a shipping rate.
The easiest solution to this issue is to make sure that when you create your rates that you have an "Everything Else" rate, which is the default shipping rate that will be used if a specific country or region isn't specified.
To view all of your shipping rates you have created, click on the "Shipping Rates" tab under your store: