I think Firefox is not able to validate the validity of the certificate of the website, try adding an exception.

Thank you for the suggestion. When this happens, there isn't an option on the page to add an exception (I read that suggestion on the help page), do you know where to do this?

Here check this problem , i think you issue is duplicate of this https://support.mozilla.org/en-US/questions/971951?esab=a&s=add+exception&r=0&as=s

That site works for me in Firefox 24.

• https://shapetoronto.antaris.ca/

DigiCert High Assurance EV Root CA
DigiCert High Assurance CA-3
*.antaris.ca

You can 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.

If that didn't help then remove or rename secmod.db (secmod.db.old) as well.

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

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox

i think its a problem with validation,better update and check weather its working or not!! thank you.