Hi Jack. I'm Greg, an Independent Advisor.
If you're sure everything was put in right, and the same card works online elsewhere, then it is likely a server problem so I would try again later.
If you cannot get it to work then contact Support at https://support.microsoft.com/help/4051701/glob... or at https://support.microsoft.com/contactus choose Get Help, then Contact Us toward the bottom, then answer Yes you can Sign In, then Select Product: Windows, then tell the Issue, it should offer Messaging and/or a Call Back on week days.
Keep me posted on your progress as I will be here to help until the case is resolved.