Find the answer to your question
Why do I receive a Credit Card error when registering a Sandbox seller?
The Sandbox site will request you to enter Credit Card or Bank Account information if you attempt to manually register your test user as a seller. Do not attempt to complete this step.
How to Register a Sandbox User as a Seller
Errors seen when a User is not a registered Seller
If your sandbox user is not a registered seller, you may see the following types of errors: