If you visit websites and Firefox does not load the website. Instead, Firefox shows you the error message “Your connection is not secure”, “SEC_ERROR_UNKNOWN_ISSUER”.
Then it is advisable to perform the following steps to solve the SSL (Secure Socket Layer) certificate connection problem.
Your connection is not secure is due to a trust issue with the SSL certificate on the website you are visiting, which is preventing Firefox from loading the entire website successfully.
Your connection is not secure is basically a protection against misconfigured websites to prevent Firefox from visiting a website that could steal information through a “man in the middle” attack.
It's complicated protection, but the solution is usually simple, just follow the instructions below.
Fix your connection is not secure message in Firefox
Open Firefox, if you haven't already. In the address bar type: about:config
Accept the risk in the warning screen and proceed with Firefox configuration settings.
Use the Windows certificate store
In the search bar type: security.enterprise_roots.enabled
Change the boolean type from false to true by double clicking. After the adjustment, Firefox can trust and use the Windows Certificate Store.
Restart Firefox for the changes to take effect and see if the “your connection is not secure” error in Firefox is resolved.
Reset Firefox settings
You can reset Firefox settings if the problem is not resolved.
Resetting Firefox will reset all settings to default as if you had just installed Firefox. This can help you resolve the root cause of the “your connection is not secure” message.
After resetting Firefox, you can find your old Firefox data in a folder called “Old Firefox Data” on your Windows desktop.
How to Recover Old Firefox Data.
In the address bar type: about:support
Click the Refresh Firefox button in the “Optimize Firefox” section. Confirm the reset by clicking Refresh Firefox in the confirmation window.
I hope this article helped resolve the: Your connection is not secure message in Firefox.