Fix · Cloudflare
Fix “TLS certificate validity” on Cloudflare
Install a valid certificate from a trusted CA (free via Let's Encrypt) covering this exact hostname, and keep the chain complete.
No server-level snippet for this control on Cloudflare; apply the guidance below.
Verify the fix
Re-run the TLS certificate validity check after deploying. Test config changes in staging first and keep a rollback: a wrong header can break a site faster than a missing one.
Other stacks: nginx · Apache · Caddy · Express / Node