Invalid SSL certificate
A valid certificate is what makes HTTPS trustworthy. When it is expired or mismatched, browsers show a full-page security warning that stops most visitors.
What it is
This check flags certificates that are expired, self-signed, issued for a different hostname, or part of an incomplete chain.
Why it matters for SEO
A blocked HTTPS handshake means users and often crawlers never reach the page, so traffic and indexing collapse until it is fixed.
Example
ERR_CERT_DATE_INVALID - certificate expired 12 days ago
ERR_CERT_COMMON_NAME_INVALID - issued for www. but served on apex
How to fix
- Renew the certificate before it expires; automate renewal.
- Cover every hostname you serve (apex and www, or a wildcard).
- Install the full intermediate chain, not just the leaf.
- Verify with an SSL checker, then re-crawl.