My credit card is valid, but I'm still getting Amazon Prime error 3565. What should I do?

Even with a valid credit card, the error could stem from Amazon's system. Try removing the card and adding it again. You could also try using a different payment method, such as a debit card or gift card. If that doesn't work, contact Amazon customer service directly through their website or app for further assistance. They may be able to identify a specific issue with your account or payment processing.