For some reason the fields to input the card information only show up once you've logged out of your account. Thats what happened for me anyway, i was trying to purchase a dlc for a game I've been following for years, and like you all, nothing popped up. When i logged out of my account and tried again, it had me sign in again and then allowed the fields to pop up. Weird though, it's never happened before.... hope that helps you guys