My credit card could not be verified but I am certain it is a valid card. What could be the problem? takes utmost care on preventing fraudulent credit card transactions. If your credit card was declined, it may be one of several things.

The information that you have entered might not be verifiable.
Please verify that you are entering your billing address correctly. Your billing has to match your credit card's billing address.

You might have reached the credit limit of your credit card.
Please use a different credit card.