dhonions,
Please do not create a new Creative Cloud account with a different email address, as this will cause other problems down the line. There has been an issue with the page on Adobe's website, and we are working to resolve that. I have had confirmation from Adobe IT that this issue was resolved early this morning US time, and I have tried it successfully on my own account, so I'd like to check in with you on a few things:
1) Can you tell me what country your account is tied to?
2) At what point exactly are you getting the 404 error? Is it when you click "Edit billing" or is it after you have entered your updated credit card information?
I know that the navigation in the North American store is a bit different than the navigation in other regions, but in case the navigation that I can see on my end works better than the link in your email, I will share it here:
Login to MyAdobe > Go to My Products and Services > Select the link next to your Creative Cloud Membership that says "Active," "Manage," or "Renew" > Click the link to Edit billing.
If this doesn't work for you, please let me know directly at my email address which I am spelling out here (bfink at adobe dot com), and I will continue to work with the Adobe IT group to resolve this. In addition, you can feel free to call the Customer Service phone number that is appropriate for your region.
Thank you!
Barbie Fink (Adobe Customer Experience Improvement Leader)