How to fix “Comodo RSA Certification Authority Not Trusted” error

A simple fix for an uncommon error

If you’re getting an error message on your browser that says, “Comodo RSA Certification Authority Not Trusted,” it means that whatever browser you’re using doesn’t have the proper Comodo root certificate in its trust store. This is not a common problem, but it does occasionally happen. There’s a simple fix, too.

Why does the Comodo RSA Certification Authority Not Trusted error occur?

Every browser uses what is called a root store or a trust store as the basis for authenticating SSL certificates. This Trust Store contains roots from all of the Certificate Authorities that the browser trusts to issue SSL/TLS certificates. Google, Mozilla, Apple– they all have their own trust store programs that continuously audit CAs to ensure compliance and protect the whole ecosystem.

When your browser arrives at a website with an SSL certificate, your browser goes through a process where it tries to chain the server certificate back to one of the roots in its Trust Store. This is why sometimes SSL certificates are sent with intermediate certificates– you have to build a chain of certificates that a browser can trace back to a root in its store.

The problem you’re having is that when you visited whatever site(s) you’re having the issue with, the SSL certificate attempt to chain back to a Comodo root that is no longer in your Trust store. Browsers and OSs typically give you the ability to edit what’s in the trust store in case you want to add a root. Unfortunately, sometimes you can accidentally delete one, too. Comodo is universally trusted and its roots are ubiquitous across all browsers, unless they’ve been deleted by the user.

How do I fix the Comodo RSA Certification Authority Not Trusted error?

Well, there are two ways. You could figure out which Root it is that you’re missing, head over to one of Comodo’s support sites, download the root and add it yourself. Or you could do it the easy way.

Here’s the easy way, whatever browser you’re using, go in and back up anything that needs backing up, clear all of your settings and then delete it from your computer. The whole browser. Delete it.

Now, go to the vendor’s site and download it again.

The Comodo Root will now be restored to your Trust Store.