Unable to create iOS App Development certificate
There have been outages to several Apple online services. Sadly, I've seen errors even when the system status is green.


https://developer.apple.com/system-status/


Your best bet is to wait it out if you can. If you cannot, you'll need to open a support ticket to speak with someone that has visibility on the server side. While you're waiting, try safari in private browsing and/or use a different web client to be sure it's not a bad cookie or something browser related.