SSL & HTTPS | Updated January 2026
The "Secure Connection Failed" error in Firefox means the browser cannot establish an encrypted connection to the server. The error message usually includes technical details like "SSL received a record that exceeded the maximum permissible length."
Most Likely Cause
SSL certificate is missing or misconfigured
Check your SSL status in cPanel > Security > SSL/TLS Status. If your domain does not have a certificate, click "Run AutoSSL" to generate a free one. If it shows as valid but Firefox still errors, clear your browser cache and try again.
01. Other Causes
- Mixed HTTP/HTTPS configuration - Your site may be trying to serve HTTPS content over port 80, or vice versa. Make sure your site URL uses
https://consistently. - Firewall or antivirus interference - Some security software intercepts HTTPS connections. Try temporarily disabling your antivirus SSL scanning to test.
- Outdated browser - Very old Firefox versions may not support the TLS version the server requires. Update Firefox to the latest version.
- Cloudflare SSL mode - If you use Cloudflare, make sure the SSL mode is set to "Full (Strict)," not "Flexible." See Cloudflare Guide.
For the Chrome equivalent of this error, see ERR_SSL_VERSION_OR_CIPHER_MISMATCH. For general SSL setup, see SSL Certificates and HTTPS.
SSL Issues?
Open a Support TicketQuick Recap
- Check SSL/TLS Status in cPanel and run AutoSSL if needed
- Clear browser cache after certificate changes
- Check Cloudflare SSL mode if using Cloudflare
- Update Firefox to the latest version
- Disable antivirus SSL scanning to test
SSL troubleshooting · Last updated March 2026 · Browse all SSL articles
