I own uaccb.site. It is a legit domain and site but, after a bit of a wait I get the error “uaccb.site is not a registered domain”.
That domain is showing the following error which may be blocking any changes to that domain:
While you look into that, open a Support Ticket here. Some TLDs can be finicky when trying to add them to Cloudflare.
Login to Cloudflare and then contact Cloudflare Support by clicking on the Get More Help button.