My Apple ID won’t let me download free apps without putting in a payment method

I go to download apps on my iPad and it asks for my Apple ID password as normal.

I click continue and it comes up with vertification required and takes me to payment method.

After I complete all of my credit card details (because it refuses to let me leave as none, even though I’m downloading a free app) it tells me my card is unable to be verified.

I know for a fact that my card works, and seeing as it’s a free app the amount of money on my card shouldn’t effect it. How can I fix this, so that I’m able to download FREE apps again?