The answer
A registered domain does not display a website on its own. It needs a configured website destination and matching DNS records. Errors can also result from a domain not yet added to the website service or a missing HTTPS certificate.
What to do
Check that registration is complete and the domain appears in your account.
Compare active nameservers and A, AAAA or CNAME values with your website instructions.
Test the root domain and www; do not bypass certificate warnings.
Send support the domain, exact URL, error message and time of the last change.