As usual, @Medic is correct. I will elaborate a bit so that you understand what Amazon has done to you.

This is one of the great flaws in the Amazon system. You can OPEN an Amazon account with a DEBIT card but when you go to the next step and want to be a seller you need a credit card.

IF Amazon was interested in ANYTHING other than cash flow (for them) they would verify that applicants for a SELLING account had a VALID credit card on file BEFORE they allowed an account to be opened.

Amazon is NOT interested in correcting that issue because they collect $40 EVERY TIME a "seller" opens an account and then does NOT have a valid card that they can use on the site.

THOUSANDS of "new sellers" every month and HUNDREDS that don't have (initially) the proper cards on file. And that translates to MILLIONS of dollars a year for (you guessed it) AMAZON.

Here are the steps on the Amazon "help" board for fixing the issue IF you have a valid card to use:

Update your credit card information

If you have received an error message about your credit card, it is important to update your credit card information as soon as possible.

Check the below information related to your credit card:

Is the credit card valid?

Is there a minimum charge amount?

Are you using a pre-paid card? (Note: Use of a pre-paid card is not accepted for a selling account.)

Does the bank have a record of the charge attempt?

Are there bank limits or policies that prevent the charge attempt from being authorized?

Is there any incorrect credit card information entered? (Note: All the credit card information entered such as number, name, address, ZIP code, or expiration date must be an exact match with your card details.)

Is this chargeable in the currency of the Amazon marketplace where you registered your seller account?

Until the card verification problem is resolved, Amazon won't be able to process any payments for your account.

Note: Only the primary account owner can make changes related to payment information.