First, please verify the following:

1. The name and billing address you're using to subscribe match the name and billing address for the credit card.*
2. The credit card number is entered correctly.
3. The expiration date is valid.

If all information was entered correctly, then you will need to check with your bank as to why the card was declined. It usually can mean incomplete address information or insufficient funds.

*Note: The name and address on your resume do not necessarily need to match the subscription address.