Please ask your client following:
Please contact your credit card issuer/bank at their 24/7 phone number and ask them for the reason they are not authorizing your payment to
www.joomlapolis.com
.
They will be able to tell you and normally to fix the issue within minutes, so that you can just re-try. Sometimes they block international payments until you call, but they can block for a variety of reasons. They can tell you the reason for sure.
Alternatively, you can pay through Paypal and 2Checkout as backup methods with a credit card without creating accounts there.