Why can't I buy books in Apple Books anymore?

I can’t buy free books either. I tried changing my Apple ID password, signing out on my phone, signing out of Books and re-adding my card to Wallet. It’s still registered for Apple Pay so I don’t understand what the problem is?

Is it because I activated Visa Click To Pay? I deactivated it again, before everything else above, but it’s still not working. It’s not working on neither of my iPhone, iPad or MacBook Air.

[Re-Titled by Moderator]