Hi Norm1,

You should take a look at the "This Connection is Untrusted" error message appears - What to do Knowledge Base article. There are some great troubleshooting tips in there. It could be as simple as the fact that your computer clock is incorrect.

Hopefully this helps!

Try to rename the cert8.db file in the Firefox profile folder to cert8.db.old or delete the cert8.db file to remove intermediate certificates that Firefox has stored.
If you have user certificates that you want to keep then export those certificates to a .cer file before removing the cert8.db file.
If that helped to solve the problem then you can remove the renamed cert8.db.old file.
Otherwise you can rename (or copy) the cert8.db.old file to cert8.db to restore the previous intermediate certificates.
Firefox will automatically store intermediate certificates when you visit websites that send such a certificate.

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder