More often than not, card transactions are refused because of mistakes made in the information submitted (for example, if the billing post code does not match the bank records or if the CVV code was incorrect), but some transactions are refused because of restrictions in the use of the card.
For example, if you are based in the USA, your payment attempt via the "Visa, Mastercard, American Express" credit card payment option was refused and you are certain that the information submitted was correct, one possibility may be that your card is restricted to local (US) transactions and cannot be used to pay an overseas merchant. Our corporate headquarters is in Singapore and your card must allow overseas transaction for the payment to go through.
Many debit and prepaid cards are restricted in such a way.
One way to put the transaction through will be to select "PayPal" in "Payment Information" at Checkout. Payments via PayPal can be made using any valid credit, debit or prepaid card, you do not need to have a PayPal account, and this payment method usually works better with restrictive credit, debit and prepaid cards.
If PayPal payment does not work either, please contact your bank for more information on the declined charge.