With the SlickAlpha NS Checker tool, you can check nameserver entries from the public DNS cache against authoritative nameservers from the domain registry.
If the public nameservers are empty, and it has been 72 hours since the last change, authoritative nameservers may not be resolving your DNS queries. This can be fixed by contacting the DNS hosting provider indicated on "Registered nameservers".
If authoritative nameservers (WHOIS nameservers) are empty, it may indicate an expired domain or other domain system errors. This can be checked by confirming the domain's validity and its nameservers on the domain registrar platform where the domain is registered.
If the records do not match, the DNS resolution may fail, and websites and other internet properties that depend on it may become unreachable.