If Beanstream or Paypal (our credit card processors) report "payment unsuccessful", "declined" or "entered information cannot be authenticated" or similar error messages, then this is not a technical glitch or an "error" message, rather, this is a message indicating that your credit card was declined by your bank. First, double-check the information you entered (credit card number, expiration date, number at the back of the card, postal code etc.).
If the problem persists you must use a different credit card or contact the credit card issuing bank to inquire why the credit card was declined. Sometimes the card is over limit, sometimes it is just a "security feature" because the card was processed in a different country. Unfortunately, all we know at our end is that the card was declined and to find out why, you need to call the bank (phone number is usually on the back of your card).
Please contact us at firstname.lastname@example.org with a screenshot only if you continue having problems to pay after your bank confirmed that the card should have gone through and/or after trying other cards. Note that we only accept Mastercard or Visa (not AMEX).