A list of common reasons why payments fail:
Your credit card limit was reached (insufficient funds) Check your credit limit. You might have reached your daily or total credit card limit on the day you tried to charge your card. If this is the case, ask your credit card company to increase your limit.
The charge exceeded the maximum amount allowed for a single charge
Check the maximum amount your card can be charged at a single time. If the declined charge is higher than this amount, ask your credit card company to increase the limit
Your card reached the maximum number of charges allowed in a period:
Check how many times your card can be charged in given time period. If you reached this amount, ask your bank to increase the limit, wait until your card can be charged again, or make a payment with a different payment method. Your card doesn't accept charges from an online source Make sure your card allows online transactions. If it doesn't, talk to your credit card company about allowing these charges. Or use another card
Your card doesn't allow international transactions If you're making payments from abroad, make sure your card accepts international charges. If it doesn't, ask your bank to change this or use another card.
Your card is not authorized for transactions of the classification type MO/TO contact your financial institution to allow transactions of classification type MO/TO (which stands for mail order/telephone order)
Wrong expiration date Review the expiration date on your credit card. If your card expired, use another card Wrong credit card number You should get an error message indicating the card number is not valid. If not, carefully check the card number when filling out the form.
Billing address Make sure that the billing address you use for the transaction matches those that your credit card company has. Address matching is however not very likely