Hello,

Sorry to see this is going on for you! Have you tried to give Mozilla feed back by using the following link: https://input.mozilla.org/en-US/feedback/

From,

Sir.Mayo

I have not but will now, Thank You.

Hello,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.

Firefox never includes intermediate certificates. It is the responsibility of a server to include all required intermediate certificate to make it possible to build a certificate chain that ends with a built-in trusted root certificate.

Note that Firefox automatically stores intermediate certificates that servers send in the Certificate Manager for future usage (they appear labeled as "Software Security Device" in the Authorities tab). If a server doesn't send a full certificate chain then you won't get an untrusted error when Firefox has stored missing intermediate certificates from visiting a server in the past that has send it, but you do get an untrusted error if this intermediate certificate isn't stored yet.