Welcome to the Godaddy community! We're not reporting any issues with the Domain Control Center, so you may want to try this action in a private, or incognito browsing window to avoid any caching from your previous actions. If you still aren't able to add this record, please contact our customer support team. You may have an underlying issue due to other conflicting records on your DNS.
TLH - GoDaddy | Community Moderator Supporting you at x.co/247support