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.

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

Firefox will not reopen

  • 1 reply
  • 1 has this problem
  • 13 views
  • Last reply by Scott

more options

Message: Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window.

Windows 11 version 21H2, build 22000.434

Message: Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window. Windows 11 version 21H2, build 22000.434

All Replies (1)

more options

Ok found the Parent.Lock file (not easily) and deleted it. Why is this still happening after 6-7 years?