The regulation for purchases for electronic goods within the European Union changed with 1.1.2015. Purchases are now subject to the VAT tax rate of the country where the order is originating from. To ensure this the European Union requires two pieces of information to proof that your purchase is actually coming from this country.
Please do one of the following:
Enter a correct VAT ID and purchase again
Make sure your billing address matches your location and purchase again
Send an email to firstname.lastname@example.org for clarification