Firefox for Desktop suddenly unable to establish secure connection with websites

'''Current Setup:''' OS: Windows 11 Home (10.0.26200) Firefox Version: 151.0.2 (Build ID: 20260525130955) '''Issue:''' * Firefox suddenly is unable to connect to '''any''' wesbite * All attempts to browse result in the "Secure Connection Failed" screen * All other browsers function fine with no network connectivity issues '''Exact Display Text:''' Secure Connection Failed The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. What can you do about it? The issue is most likely with the website, and there is nothing you can do to resolve it. You can notify the website’s administrator about the problem. '''Attempted Fixes / Things Confirmed:''' * Everything mentioned in: [[Firefox can't load websites but other browsers can|Firefox can't load websites but other browsers can]] * Relevant ''about:config'' values: ''* * security.enterprise_roots.enabled -> True * * security.ssl.enable_ocsp_must_staple -> True * * security.ssl.enable_ocsp_stapling -> True * * security.tls.version.max -> 4 * * security.tls.version.min -> 3'' * System locale and timezone are correct * DNS over HTTPS is set to OFF * HTTPS-Only Mode is set to Don't enable HTTPS-Only Mode * Restarting in Troubleshooting Mode * Disabling the Anti-Virus (including the device Firewall) * Disabling any VPNs or network proxies * Clearing cache and browsing history * Clearing certificates from the Certificate Manager in Settings * Attempting connection with a newly created profile * Clearing the cert9.db file for Firefox to reset certificate information * Refreshing Firefox (resetting it completely) * Uninstalling and reinstalling Firefox (after clearing all Mozilla related %appdata% folders) '''Observations''' * When trying to mess with the device timezone and see if changing it back to the correct one would "reset" something, after a few attempts of starting Firefox in the wrong timezone and then restarting it after changing to the correct one, for a single session, I was able to browse normally again. I closed Firefox to see if the problem was fixed but it went back to the "Secure Connection Failed" page. Was unable to reproduce the same behavior. * Tried installing a portable version of Firefox (151.0.3) from [https://portableapps.com/apps/internet/firefox_portable Firefox Portable] . After installation, the first session works perfectly fine but after I close the session and restart Firefox, it gives the same "Secure Connection Failed" message. * * Reinstalling the portable version in the folder, gives the error from the get-go, not even the initial post-installation session works but installing in a different folder works fine for the first session but all subsequent restarts (sessions) of the browser give the same error.