Periodically when Firefox is updated, it starts rejecting Yahoo Mail from loading, giving the "Your connection is not secure" / SEC_ERROR_UNKNOWN_ISSUER error. Unfortuna… (read more)
Periodically when Firefox is updated, it starts rejecting Yahoo Mail from loading, giving the "Your connection is not secure" / SEC_ERROR_UNKNOWN_ISSUER error. Unfortunately, it does not give you the option to add an exception, which clears up the problem most of the time.
Today this happened again with no ability to add an exception, and after looking at various websites for hours, trying to find a fix, I stumbled on one: Having Firefox "...automatically search for and import CAs that have been added to the Windows certificate store by a user or administrator." These are root certificates which you've manually imported. If you understood that last sentence, then it means you've probably done it on your computer; I know I have. The steps to fix it are these, and I cite the original web page further below:
- Open a new window in Firefox and type "about:config" without the quotes and hit enter - Confirm that you want to continue - In the search field, type in security.enterprise_roots.enabled and hit enter - you'll be left with one field - If it's marked as "false" then double-clicking it should turn it to "true" - Close the window, then go back to your Yahoo email login and try again. For me, this worked *perfectly*!
Here's the site where I found the info, under the "Experimental Built-in Windows Support" section: https://wiki.mozilla.org/CA:AddRootToFirefox
Good luck - I hope this helps to fix your Yahoo email login problem, too!