Member Avatar for vertigo21

I am using the latest version of Firefox and it will not allow me to log into certain sites that I am regitered for. This problem boggles me because it allows me to log into some sites but not others. What is the problem?

Vertigo21

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For : since Firefox accepts some logins but not others, the next steps should be diagnostic and evidence-based rather than guessing. and point toward client/server differences; below are focused checks and things to look for that are commonly missed.

Quick diagnostic checklist

  • Try a Private Window and then a clean Troubleshoot Mode (restart with add-ons disabled).
  • Test the same sites in another browser on the same PC and on a different device/network. If they work elsewhere, the problem is local to this Firefox profile or machine.
  • Clear site-specific cookies and cached data for the failing domains (delete cookies and site data).
  • Create and test with a new Firefox profile (about:profiles) or use Refresh if the profile seems corrupted (Refresh Firefox).

If the quick checks fail, gather evidence

  • Open Developer Tools (F12) -> Network and Console. Watch the login POST and follow-up redirects. Look for 4xx/5xx responses, blocked resources, CORS or “mixed content” errors. The Network Monitor docs help with this: Network Monitor.
  • Check whether cookies set on login are actually sent on subsequent requests. Modern cross-site flows often rely on cookies with SameSite=None and Secure — if those are blocked you’ll see the session never establish. Read about SameSite attributes here: SameSite cookies.

Other common causes to inspect

  • Intercepting proxies/antivirus that replace certificates (inspect the site certificate chain in the padlock UI). See guidance on TLS/SSL failures: Secure connection failed.
  • Sites that require legacy, platform-specific auth (SSO/NTLM/Active Directory) or server-side blocks — if the site works only from certain networks, contact the site admin with the logs you captured.

A simple header check you can run from the command line:

curl -I -L https://example.com/login

Do not put credentials into test commands; use them only to inspect headers, redirects and certificate chains.

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Member Avatar for Johnathan

There can be two problems that I know of one would be that one of the security tools that comes with firefox will automaticly block sites it determines to be bad the second is your packet size. Rescently some companies have reduced the size of the packet your computer must send in order to log in for security reasons try adjucting your packets and see if that helps.

Member Avatar for MidiMagic

Another possibility is that they use plug-ins which work in IE, but not Firefox. (Another Microsift monopoly ploy?)

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