Are you possibly using a proxy or VPN ? You can check the connection settings. *Settings -> General -> Network: Connection -> Settings If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly. See "Firefox connection settings": *https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors *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 See also: *https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean *https://support.mozilla.org/en-US/kb/secure-connection-failed-firefox-did-not-connect *https://support.mozilla.org/en-US/kb/troubleshoot-time-errors-secure-websites