Firefox Community Forum

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.

When following a link from a news website I keep getting this message - Secure Connection Failed - The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. It loads on my iPhone and other browsers using the same link. What setting do I need to address to get this to stop?

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.

I just installed Firefox on my PC haven't had it on this computer since reinstalling windows - I imported my bookmarks and passwords from Edge, thinking it would be a seamless transition, since I used Firefox in the past without much trouble.

Two weeks on, about 95% of every page I open gives an error similar to the one below, and I have to shift+refresh several times to get it to reload before it goes away, (some sites still don't open).

I wonder how common this issue is, and how people fixed it?

Be careful. Something doesn't look right.

Firefox spotted a potentially serious security issue with connect.mozilla.org. Someone pretending to be the site could try to steal things like credit card info, passwords, or emails.

Go back (Recommended)

Hide advanced

Advanced What makes the site look dangerous? The site is set up to allow only secure connections, but there's a problem with the site's certificate. It's possible that a bad actor is trying to impersonate the site. Sites use certificates issued by a certificate authority to prove they're really who they say they are. Firefox doesn't trust this site because its certificate isn't valid for connect.mozilla.org. The certificate is only valid for: *. eero.com. What can you do about it? Probably nothing, since it's likely there's a problem with the site itself. Sites use certificates issued by a certificate authority to prove they're really who they say they are. But if you're on a corporate network, your support team may have more info. If you're using antivirus software, try searching for potential conflicts or known issues. View the site's certificate Learn more about secure connection failures Error Code: SSL_ERROR_BAD_CERT_DOMAIN Jun 5, 2026 10:58:34 AM GMT+10

Proceed to connect.mozilla.org (Risky)

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.

I cannot access any site on the internet, including all that I use normally like mail and newspaper sites, medical provider websites. Neither Firefox nor Safari work--I get the same error message on both. This doesn't happen with other isp providers, like a public computer in the library, just at home. Could there be a modem or isp provider problem at my home?

Hi.

Why i need every time i restart the firefox esr accept the cudy.net certificate? Look the picture.

Is there a way to add it as exclude this certificate and NOT ask me every time i restart the firefox esr to accept this certificate?

Secure Connection Failed

An error occurred during a connection to feg.uh1.ac.ma. SSL received a record with an incorrect Message Authentication Code.

Error code: SSL_ERROR_BAD_MAC_READ

Hello!

For few minutes it says "Performing a TLS handshake to youtube.com", then this message appears:

==

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.

==

What I did so far:

1. Deleted cache and site data for youtube.com. 2. Checked if date and time setting is set to auto and synced it just in case. 3. Tried restarting firefox in safe mode. 4. Tried turning off ocsp stapling. 5. Deleted ALL cache and site data. 6. Tried creating a new profile. 7. Set HTTPS-only mode to "don't enable" and added youtube.com to exceptions

I do use DoH. I can't not use it. YT won't work without it for sure. Provider is google: https://dns.google/dns-query

Everything works fine in Chrome (yes, I use DoH there too).

Hello, I run a movie and drama-related website: https://tvmon.com.co/. Recently, I’ve noticed that Firefox occasionally throws the following error when trying to access the site:

"Secure Connection Failed An error occurred during a connection to tvmon.com.co. . The OCSP response contains an invalid signing certificate. Error code: SEC_ERROR_OCSP_INVALID_SIGNING_CERT"

This issue is very strange because:

1. The site loads fine in Chrome, Edge, and Safari.

1. My SSL/TLS certificate is valid, up-to-date, and passes external tests (SSL Labs, etc.).

1. The error only appears occasionally in Firefox, refreshing sometimes fixes it, sometimes not.

1. Hosting and server logs show no issues at all.

I suspect this is related to Firefox’s stricter OCSP validation, but I’m not sure how to debug or resolve it. Since my site streams drama and movie content, this error is frustrating for users who rely on Firefox.

Has anyone else experienced this intermittent OCSP signing certificate error? Is there a known fix or workaround for Firefox-specific validation issues?

I have been having issues where I am unable to access the website: www.loki.ch. This is the web site for a Swiss railway magazine. I have always been able to access it previously, but haven't used it now for a few months. However this week when I've tried, I'm blocked access to it (see the attached screen shots). I do note that since I had previously access the web site, there have been updates to Firefox. However, when trying to use either Edge or Google Chrome, they also block me, but just say that unable to access the web site, nothing mentioned about being "Not Secure" as Firefox does. It's not a web site where you have to log in and/or use passwords. Contacting the magazine by Facebook messenger yields no response from them. Posting the issue on a Facebook group, other users have responded that they can access it (one was from Slovenia and the other in the UK). One mentioned issues from Australia where I am. It's not a dangerous or suspect web site, simply a magazine about Swiss Model Trains. I have tried adjusting settings to exempt it in Settings - no change. Not a anti virus issue. None of the suggestions in the FAQ have exactly the same scenario in the screen shots attached.

Surely there has to be some way to bypass whatever is in Firefox Security preventing me from accessing this web site?

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

성인사이트가 크롬과 엣지에서는 정상적으로 열리는데 파이어폭스에선 보안 연결 실패라고 뜹니다. 원래 파이어폭스에선 성인사이트를 차단하고 있는 건가요? 아니면 차단을 해제할 수 있는 방법이 있는 건지요 Adult sites open normally on Chrome and Edge, but on Firefox it says security connection failure. Is Firefox originally blocking adult sites? Or is there a way to unblock it