Sometimes credit cards are declined for a variety of reasons.
1. Reasons for Declined Credit Cards
There are a few reasons why your credit card might have been declined.
One reason is that the expiration date and/or the 3 or 4 digit card security code was not correct for the card number. Please verify that the expiration date and card security code are both correct for the card you are using.
The expiration date on the credit card is the end date of your card. For example, if your card is valid from Jan 2015 - Dec 2018, please enter the expiration date as 12/18.
The card security code for Visa and MasterCard is the 3 digit code on the back of the card near the signature section. The security code for American Express is the 4 digit code on the front of the card (last 4 digits).
Another reason might be that the card was not accepting online transactions and so was declined. That might be that your card company does not allow the card to be used for online transactions or that it was declined for another reason such as a hold, insufficient credit limit, etc.
If you can, please try another credit card.