How to Fix Common SSL Certificate Errors on Your Website

Secure Sockets Layer (SSL) certificates protect your website by encrypting data between your server and visitors. When SSL certificates fail or show errors, visitors see warnings that can scare them away and damage your site’s credibility. Fixing these errors quickly is essential to keep your website trustworthy and safe.

This guide explains the most common SSL certificate errors and how to fix them step-by-step. Whether you run a small blog or an online store, understanding these issues helps you maintain a secure connection for your users.

SSL padlock icon indicating secure connection

What Causes SSL Certificate Errors

SSL certificate errors happen when browsers detect problems with the certificate or the connection. These errors can appear as warnings like “Your connection is not private,” “SSL certificate expired,” or “Certificate not trusted.” Common causes include:

• Expired certificates: Certificates have a validity period. If yours expires, browsers warn visitors.

• Mismatched domain names: The certificate must match the website’s domain exactly.

• Untrusted certificate authority (CA): Browsers trust certificates issued by recognized CAs only.

• Incomplete certificate chain: Missing intermediate certificates can cause trust issues.

• Incorrect server configuration: Misconfigured servers may not serve the certificate properly.

  
  

Understanding these causes helps you identify the right fix.

How to Check Your SSL Certificate Status

Before fixing errors, confirm your SSL certificate’s status using these tools:

• SSL Labs’ SSL Test (https://www.ssllabs.com/ssltest/): Enter your domain to get a detailed report on your certificate and server setup.

• Browser inspection: Click the padlock icon in your browser’s address bar to view certificate details.

• Command line tools: Use `openssl` commands to inspect certificates directly from your server.

  
  

These checks reveal if your certificate is expired, mismatched, or missing intermediate certificates.

Fixing Expired SSL Certificates

Expired certificates are the most common cause of SSL errors. Here’s how to fix them:

1. Renew your SSL certificate: Contact your certificate provider or use your hosting control panel to renew.

2. Install the renewed certificate: Upload the new certificate files to your server.

3. Restart your web server: Apply changes by restarting Apache, Nginx, or your web server software.

4. Verify installation: Use SSL testing tools to confirm the new certificate is active.

   
   

Renew certificates before they expire to avoid downtime. Many providers offer automatic renewal options.

Resolving Domain Name Mismatch Errors

If your certificate does not match your website’s domain, browsers will show errors. Fix this by:

• Checking the certificate’s common name (CN): It must match your domain exactly, including subdomains.

• Using Subject Alternative Names (SANs): Certificates can cover multiple domains or subdomains.

• Purchasing a wildcard certificate: This covers all subdomains under a domain (e.g., *.example.com).

• Reissuing the certificate: If the domain changed, request a new certificate with the correct domain.

  
  

Make sure you use the exact domain visitors use, including “www” or non-www versions.

Fixing Untrusted Certificate Authority Issues

Browsers trust certificates issued by recognized authorities. If your certificate is self-signed or from an unknown CA, visitors see warnings. To fix this:

• Buy certificates from trusted CAs: Use providers like Let’s Encrypt, DigiCert, or Comodo.

• Avoid self-signed certificates for public sites: These are only suitable for testing or internal use.

• Check for revoked certificates: If your CA revoked your certificate, get a new one immediately.

  
  

Using a trusted CA ensures browsers accept your certificate without warnings.

Server rack showing active web hosting environment

Completing the Certificate Chain

SSL certificates often require intermediate certificates to link your certificate to a trusted root CA. Missing these intermediates causes errors. Fix this by:

• Downloading intermediate certificates from your CA: They usually provide these files.

• Installing intermediate certificates on your server: Combine them with your main certificate if needed.

• Configuring your server to serve the full chain: Check your web server’s SSL configuration files.

• Testing with SSL tools: Confirm the full chain is served correctly.

  
  

Proper chain installation prevents trust errors and improves compatibility.

Correcting Server Configuration Issues

Sometimes SSL errors come from server misconfiguration. Common problems include:

• Serving the wrong certificate: Your server might send a default or expired certificate.

• Incorrect SSL protocols or cipher suites: Outdated protocols can cause errors or warnings.

• Missing HTTPS redirects: Visitors may access the site via HTTP, causing mixed content warnings.

  
  

To fix these:

• Review your server’s SSL settings: Check Apache’s `ssl.conf` or Nginx’s `nginx.conf`.

• Enable strong protocols like TLS 1.2 or 1.3: Disable older versions like SSL 3.0.

• Set up automatic HTTP to HTTPS redirects: Use `.htaccess` or server rules.

• Test your site after changes: Use browsers and SSL testing tools.

  
  

Proper configuration ensures a smooth, secure connection.

Handling Mixed Content Warnings

Even with a valid SSL certificate, your site may show warnings if some resources load over HTTP instead of HTTPS. This is called mixed content. Fix it by:

• Updating URLs in your website code: Change all links, images, scripts, and stylesheets to HTTPS.

• Using relative URLs: This avoids hardcoding HTTP or HTTPS.

• Checking third-party content: Ensure external resources support HTTPS.

• Testing pages with browser developer tools: Look for mixed content warnings.

  
  

Eliminating mixed content keeps your site fully secure and trusted.

Code editor displaying HTTPS URLs in website source code

Tips to Prevent SSL Certificate Errors

Avoid SSL errors by following these best practices:

• Set reminders for certificate renewal: Renew certificates well before expiration.

• Use automated tools: Services like Let’s Encrypt offer free certificates with automatic renewal.

• Monitor your website regularly: Use uptime and SSL monitoring tools.

• Keep your server software updated: Security patches improve SSL handling.

• Use a single certificate for all domains or subdomains: Simplifies management.

• Test your SSL setup after changes: Catch errors early.

  
  

Regular maintenance keeps your site secure and visitors confident.

Frequently Asked Questions

1. What is the difference between SSL and TLS certificates?

The term “SSL certificate” is still commonly used, but modern secure websites actually rely on TLS (Transport Layer Security). SSL is an older technology that has been replaced by more secure TLS protocols.

2. Why does my SSL certificate work on one browser but not another?

Different browsers and operating systems can have different trusted root certificate stores and compatibility requirements. An outdated browser, missing intermediate certificate, or unusual server configuration may therefore produce an error for some visitors but not others.

3. Why does my website still show “Not Secure” after installing an SSL certificate?

This can happen when the certificate is installed incorrectly, the page contains insecure HTTP resources, HTTPS redirects are missing, or the browser has cached an older version of the site. Check both the certificate configuration and individual page resources.

4. What does NET::ERR_CERT_AUTHORITY_INVALID mean?

This browser error indicates that the certificate cannot be linked to a certificate authority the browser trusts. It can occur with self-signed certificates, improperly installed certificate chains, or certificates issued by an unrecognized authority.

5. What does NET::ERR_CERT_DATE_INVALID mean?

This error generally indicates a problem involving certificate validity dates. The certificate may have expired or may not yet be valid. An incorrect date or time on the user's device can sometimes produce a similar warning.

6. Can DNS changes cause SSL certificate errors?

Yes. After changing DNS records or moving a website to a different server, visitors may temporarily reach a server that does not have the correct certificate installed. DNS propagation and incorrect DNS records can contribute to these problems.

7. Can a CDN cause an SSL certificate error?

Yes. Services such as CDNs and reverse proxies can have their own SSL/TLS configuration. A certificate problem between the visitor and CDN—or between the CDN and origin server—can result in HTTPS errors even when one side is configured correctly.

8. Does an SSL certificate improve SEO rankings?

HTTPS is a Google ranking signal, but installing an SSL certificate alone does not guarantee a significant ranking improvement. HTTPS is more importantly a security and trust standard, and it helps ensure that data exchanged between visitors and your website is encrypted.

9. Can I use one SSL certificate for multiple websites?

Yes. A multi-domain or SAN certificate can secure multiple specified domain names. Wildcard certificates can secure multiple subdomains of a particular domain, depending on how the certificate is configured.

10. What should I do if an SSL error appears only for some users?

Check whether the problem is associated with particular browsers, operating systems, networks, or devices. Certificate-chain compatibility, cached certificates, incorrect device clocks, DNS differences, and older software can all cause SSL errors that affect only some visitors.