If you expand the "Technical Details" section of the error, what does that show?

When there is no Add Exception button, it usually indicates that the error page is in a frame within another page. Because you can't see the true URL of the framed page, Firefox suppresses the Add Exception button to avoid deception.

The workaround is to right-click the error page > This Frame > Open in a New Tab. When the page is not framed, you should be able to add an exception, assuming you trust the server.

Then close the unneeded tab and reload the "real" page to proceed.

But... if you are getting certificate error pages from a lot of sites, we should investigate whether there is a configuration issue with your security software or potential malware on your computer.

Check the date and time in the clock on your computer: (double) click the clock icon on the Windows Taskbar.

Check out why the site is untrusted and click "Technical Details to expand this section.
If the certificate is not trusted because no issuer chain was provided (sec_error_unknown_issuer) then see if you can install this intermediate certificate from another source.

You can retrieve the certificate and check details like who issued certificates and expiration dates of certificates.

• Click the link at the bottom of the error page: "I Understand the Risks"

Let Firefox retrieve the certificate: "Add Exception" -> "Get Certificate".

• Click the "View..." button and inspect the certificate and check who is the issuer of the certificate.

You can see more Details like intermediate certificates that are used in the Details pane.

If "I Understand the Risks" is missing then this page may be opened in an (i)frame and in that case try the right-click context menu and use "This Frame: Open Frame in New Tab".

Note that some firewalls monitor (secure) connections and that programs like Sendori or FiddlerRoot can intercept connections and send their own certificate instead of the website's certificate.

Here is the deal. It is a trusted connection. Firefox thinks it isn't. I don't have the problem with Internet Explorer. As far as suppressing the exception button ... WHY? If I want to accept the risk and go forward it's my business. All of this is transpiring behind the government firewall and Lync is one of our enterprise solutions hosted internally. Anything within va.gov is trusted. Firefox has decided this to be NOT the case.

Technical Details: This Connection is Untrusted

You have asked Firefox to connect securely to vaphcclblweb.rtc.va.gov, but we can't confirm that your connection is secure.

Normally, when you try to connect securely, sites will present trusted identification to prove that you are going to the right place. However, this site's identity can't be verified. What Should I Do?

If you usually connect to this site without problems, this error could mean that someone is trying to impersonate the site, and you shouldn't continue.

vaphcclblweb.rtc.va.gov uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. (Error code: sec_error_unknown_issuer)

To Firefox, "trusted" means that it can trace the issuer of the certificate to a known authority. Either a link is missing in the chain (IE will fetch missing intermediate certificates), or your system administrators added a certificate to the Windows certificate store that IE can see but Firefox cannot see. There's no way for me to know exactly what the problem is without hands on your system. Have you asked your IT?

Regarding the missing Add Exception button, I explained the only reason I know why you might not see it. Does that explanation check out: if you right-click the error page, is there a "This Frame" entry on the menu? If so, you know what to do.

Honestly? I'm tired of all the times this happens with me. It's internal links, too. I just dropped Firefox and switched to Chrome. No issues.