Subdomains need certificates too, and they are not automatic until they exist.
HOW IT WORKS
AutoSSL covers subdomains that exist in DNS and resolve to our server. When you create a subdomain in cPanel, the DNS record is created automatically and the next AutoSSL run covers it.
AFTER CREATING A SUBDOMAIN
Run AutoSSL manually rather than waiting. cPanel > SSL/TLS Status, tick the new subdomain, and run.
WHY IT SOMETIMES FAILS
The subdomain does not resolve, usually because DNS is hosted at Cloudflare or another provider and the record was not added there The subdomain is proxied The subdomain points at a different server
FOR EXTERNAL DNS
If your nameservers point at Cloudflare, creating a subdomain in cPanel does not create the DNS record. Add it at Cloudflare, then run AutoSSL.
WILDCARD ALTERNATIVE
If you create subdomains frequently, a wildcard certificate covers them all without per-subdomain issue. For most accounts AutoSSL's approach is simpler.
CHECKING
Visit the subdomain over https and confirm no warning appears.
