Fail to add new domain

Try to add new site to cloudflare account and got this error.
What can I do ?
Thank you

We need to find a whois record and nameservers. Sorry for the issue.

Thank you.
Normally .vn , you can not find with public whois.
You can try https://vnnic.vn/whois-information

Thank you, yes, I can see the details there and can see rafe & donald as your cloudflare name servers. But, you deleted the zone from your account, can you add it back again? If we don’t detect the name servers within 24 hours, you may need to reach out to Support to have them authenticate the zone in a different way.