Please explain the problem in detail. What happens? What are the exact error message(s) ?

Thanks for your replay

when I open mqttcloud.ir in Mozilla Browser and click on connect button , show me a error massage.

butt in my home pc with Mozilla Browser when i click on connect button in this site , i ccan onnect to Mqtt Server for IOT projects.

Have you tried contacting the website support?

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

What do the security warning codes mean

Are you using "Delete cookies and site data when Firefox is closed" in case this makes a difference (service workers) ?

Any related messages in the Web Console ?

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/en-US/Tools/Web_Console

My Dear

By click in the red Alert show in the attached pitcher , security alert is opened and by accept risk of security , problem solved and now I can connect to Mqtt site

Best Regards

M.Hasanpour

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems.