Payment couldn't be processed is the most commom thing when you do online shopping. Jennyray has got a few tips to make the payment succeed.
Here's A list of common reasons why payments fail and tips to solve it:

1 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.
2 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.
3 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
4 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
5 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.
Wrong expiration date
6 Review the expiration date on your credit card. If your card expired, use another card
7 Billing address
8 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 to be the main cause of a transaction failure.
9 Your debit card has been locked by your issuing institution. This often happens when you enter an incorrect PIN at an ATM more than a few times. contact your bank to unlock the card.