Are you using a proxy? You can check the connection settings. *Options/Preferences -> Advanced -> Network : Connection -> Settings *https://support.mozilla.org/en-US/kb/Options+window+-+Advanced+panel 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/firefox-cant-load-websites-other-browsers-can