Firefox has doesn't control what Norton does or blocks that is something you need to contact Norton support on. And since there is no screenshot error no one can see what is happening. Also registered accounts are tricky that unless another user of the site uses Firefox to do login with Norton no one will know what is happening.

You can check for issues with Total Cookie Protection.

• https://support.mozilla.org/en-US/kb/total-cookie-protection-and-website-breakage-faq
• https://support.mozilla.org/en-US/kb/introducing-total-cookie-protection-standard-mode