This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

Cannot open Firefox

  • 1 reply
  • 0 have this problem
  • 1 view
  • Last reply by Terry

bsimonov
bsimonov
more options

I cannot open Firefox. Error message appears: "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window."

Task Manager always shows three active Firefox Apps, but ending those tasks does not help. I don't see any other active Mozilla procces on the list

I have uninstalled and reinstalled Firefox from MS Store but that does not help either.

I cannot open Firefox. Error message appears: "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window." Task Manager always shows three active Firefox Apps, but ending those tasks does not help. I don't see any other active Mozilla procces on the list I have uninstalled and reinstalled Firefox from MS Store but that does not help either.

All Replies (1)

Terry
Terry
more options

You may have to remove a lock file.

https://support.mozilla.org/en-US/kb/Firefox-already-running-not-responding https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data#w_finding-your-profile-without-opening-firefox