“Your connection is not private” and ERR_CERT_AUTHORITY_INVALID on Your Website

When visitors see "Your connection is not private" or ERR_CERT_AUTHORITY_INVALID, most of them leave immediately. For an online store that means lost orders. The good news is that the cause can almost always be pinpointed.

What the error means

The browser can't confirm that the site's SSL certificate was issued by a trusted authority for that domain. The problem can be on the website, or on the network the visitor is using.

Most common causes

• Expired certificate: auto-renewal failed.
• Certificate for a different name: e.g. valid for www but not the bare domain, or the other way round.
• Incomplete certificate chain: the intermediate certificate is missing, so some devices don't trust it.
• Wrong DNS or CDN/proxy configuration: the domain points to a server with a different certificate.
• A network filter or block: when a domain is blocked by a provider, visitors may be served a page with a different certificate. They see this error even though your certificate is fine.

Why it works for some and not for others

If the error only appears on a specific network, e.g. only on mobile data or only for one provider's users, your certificate is probably not the problem. Check whether the domain is blocked or redirected at network level. More in Website Blocked by A1 NetProtect?.

What we check

1. Certificate validity, expiry and hostname
2. The full certificate chain and compatibility with older devices
3. HTTPS redirects and mixed content
4. DNS records, nameservers and CDN/proxy settings
5. Behaviour from different networks and DNS resolvers

If your site shows an SSL or security warning, see Website Security & Unblocking or send us the domain for an urgent check.