Perform the suggestions mentioned in the following articles:

• Clear Cookies & Cache
• Clear the Network Cache
• Make sure that you are using the "Remember History" setting as described in this article -> Settings for privacy, browsing history and do-not-track

Check and tell if its working.

did not solve problem

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 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.

under the default tab, there is nothing in the autoconfig folder nor the profile folder

Does it make any difference if you use a direct URL:

https://complaints.donotcall.gov/complaint/complaintcheck.aspx

Same problem

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

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

This solved the problem, thanks so much for your help