Why Won't Firefox Connect to the Internet?
By David Weedmark
Updated August 23, 2018
If Firefox won't connect to the Internet, but another browser does, the problem could be with Windows Firewall, which may be blocking its access. If this isn't the problem, a rogue Firefox extension may be the culprit. If you use enhanced network security on a server, router or firewall, consult with your network administrator to see if the network might be blocking Firefox as well.
If Windows Firewall doesn't allow Firefox to connect to the Internet, you'll see a "Server Not Found" error when you try to go to a website. You can add Firefox as an allowed program by opening the Control Panel and then clicking "System Security." There you'll find the option to "Allow a program or feature through Windows Firewall." If Firefox is already listed as an allowed program, remove it from the list and then add it again as a new program.
Firefox add-ons may sometimes interfere with the browser's ability to connect to the Internet. To see if this is the problem, reset Firefox. The reset button is on the Troubleshooting Information page available from the Help menu. This disables add-ons like themes and extensions without losing your user data. If Firefox connects after the reset, you can then enable the add-ons one at a time to isolate which one was causing the problem.
A published author and professional speaker, David Weedmark has advised businesses and governments on technology, media and marketing for more than 20 years. He has taught computer science at Algonquin College, has started three successful businesses, and has written hundreds of articles for newspapers and magazines throughout Canada and the United States.