'Verify Payment' loop despite valid payment methods on App Store

i’m trying to download a free app, but every time i try it tells me to verify payment. i press continue, but it brings me to add a new payment method. i click back to see my payment methods i already have, it still tells me to verify payment, but when i click on them they are fine. i even removed my card then added it back and it still wont work. it always says the card failed, but how could it fail when it is not even being used?

[Re-Titled by Moderator]

Original Title: verify payment not working