DNS and domain issues.
ESTABLISH FIRST
Was it working before? What changed? Where is the domain registered? What nameservers is it using?
THE MOST COMMON CAUSES
Nameservers not pointing at the hosting DNS records missing or wrong The domain expired Propagation still in progress Certificate not issued
WHAT TO CHECK
Whether the domain resolves at all Where the nameservers point Whether the hosting account has the domain configured Whether the domain is expired
THE EXPIRY CHECK
Check first. An expired domain explains everything and nothing else will fix it.
FOR RECENT CHANGES
Propagation takes time. Explain that, with a realistic period.
FOR EXTERNAL DNS
If the domain uses another provider's DNS, records must be added there.
Creating a subdomain in cPanel does not make it resolve.
FOR CERTIFICATE PROBLEMS
Run AutoSSL after the domain resolves.
Order matters: the domain must resolve first.
WHAT TO EXPLAIN
What needs to happen and roughly how long.
WHEN TO ESCALATE
Anything at server or nameserver level.
