For tax reasons we need to know your location in order to process your payment, because the VAT rate on our invoice is contingent on the country you place your order in. The generally accepted procedure is to check two independent data points for identity (e.g. your IP address and the country of your payment method). If these two data points are not identical, we unfortunately have to refuse the payment.
We are very unhappy with this situation and are considering alternatives - until then we must ask you to try PayPal, where this problem (usually) does not occur.