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Beginning today, I suddenly cannot access numerous websites when I use Mozilla Firefox 151.0.2. Examples include Amazon, and Google, et al. Attempts to do so consistently fail at the point of performing a TLS handshake, when I am advised that "secure connection failed". Kindly refer to the attached screenshots. I have no difficulty whatsoever accessing the same websites when I use other browsers, such as Google Chrome and MS Edge. I previously had Mozilla Firefox enabled as my default browser, but I have had to change this, given these "challenges". Please advise how I can fix this. Best regards and many thanks.

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

• 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 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.

This message was received when I tried to follow the support link "support.mozilla.com".

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.

This is my website I work on daily - I can normally open it in this browser BUT because Im on my laptop it is flagged as a security risk - and its not - passive-income-system[.]co[.]uk

need to be able to download my old sites. and stop getting error 522 can not connect to some sites due to not secure anymore... help need to watch some movie sites.. Jose

Be careful. Something doesn’t look right.

Firefox spotted a potentially serious security issue with www.aol.fr. Someone pretending to be the site could try to steal things like credit card info, passwords, or emails. ??????? I used Aol since 1998 !!!!!!!!

I am running windows 11. I routinely use firefox to access wireclub.com. Two days ago I started getting the following error:

We encountered a problem when completing your request.

We have been notified and are attempting to fix the problem as quickly as possible.

Invalid SSL certificate

The origin web server does not have a valid SSL certificate.

   Ray ID: 9eee0086ced8439d
   Your IP address: 2600:4041:59b2:8c00:c9fa:28ce:b4cb:4bfc
   Error reference number: 526
   Cloudflare Location: Newark

I tried clearing my cache that did not work. All other sites other than wireclub.com are working fine. I can access wireclub.com with Microsoft edge no problem. Any suggestions

Secure Connection Failed

The connection to the server was reset while the page was loading.

   The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem.

Learn more… What is the reason?

Firefox will not allow me to connect to a portal I've been using for years. It gives a "SEC ERROR REVOKED CERTIFICATE" I can connect using another browser. What's up?

Secure Connection Failed

An error occurred during a connection to cow.huntforenenst.com. Peer received a valid certificate, but access was denied.

Error code: SSL_ERROR_ACCESS_DENIED_ALERT

   The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem.