Facebook signon malfunction. Complete pword and captcha. Facebook signs in on other browsers. Appears firefox is the issue

If you try logging in using new Private Window, do you see any difference?

Can you upload a screen shot of the error you're facing? Thanks.

There is no error message......... after going through the signon with userid and password.... then the aggravating captcha....it simply returns to the signon screen. I have tried with and without VPN and with and without antivirus programs. Just started a few days ago. Maybe an upgrade problem?

There doesn't seem to be anything out of the ordinary reported in terms of volumes, there were a few more broken site reports on JUN 12 and then JUN 23–24 but always tapered off within a day so it seems intermittent at Meta side.

If you're suspecting an update, you can always try pulling a separate Nightly version from any arbitrary date to test (e.g. see here for some similar experimentation), but generally this doesn't make any difference in terms of actual versions, more than coming with a separate clean profile that makes the most difference.

To rule out any "privacy" addons interfering, you'd want to restart into Troubleshoot Mode (from Help menu) and try singing in there.

Few weeks ago there were issues with Norton 360 — check if you can disable its "Safe Web" feature to see any impact.