That doesn't say anything about your payment method being declined.
Every account has to have a valid payment method unless there is a None option in the payment methods. Because only the user should know the payment method details, the system may ask for the details to verify that it is the owner actually using the account.
ASC - Late 2012 Mac mini, macOS 10.14.6; Watch, series 5 GPS/cellular, watchOS 6.2.8; iPad Air 2, ipadOS 13.6.1; iPhone 8+, iOS 13.6.1; TV 4th Gen, tvOS 13.4.8; HomePods, audioOS 13.4.8 and Airport Express w/ Airplay 2