"Firefox is already running but is not responding" error - How to fix

 All of your personal settings, bookmarks, and other information are kept in your Firefox profile. Firefox needs an unlocked profile to start up, and if the profile is locked, it displays the message, Firefox is already running, but is not responding. This article explains what to do if you see this message and how to prevent it from showing at startup. Mozilla Firefox not Responding

End Firefox processes

If Firefox did not shut down normally when you last used it, Firefox might still be running in the background, even though it is not visible. If you try to open it while it's running, an error message will appear with the option to click Close Firefox. If that doesn't solve the problem, restart your computer or try the following options.

Use the Windows Task Manager to close the existing Firefox process

1. Right-click on an empty spot in the Windows task bar and select Task Manager (or press Ctrl+Shift+Esc).
2. When the Windows Task Manager opens, select the Processes tab.

3.  Select the entry for firefox.exe (press F on the keyboard to find it) and click     End Process.

4.  Click Yes in the "Task Manager Warning" dialog that appears.

5.  Repeat the above steps to end all additional firefox.exe processes, then exit the Windows 

    Task Manager.

6.  Start Firefox normally.

Remove the profile lock file

Firefox may have shut down abnormally, leaving the lock file in place. To fix this, open the profile folder (see Finding your profile without opening Firefox) and delete the parent.lock file.

Remove the -no-remote startup option

If you start Firefox with the -no-remote command line option, try removing this option.

Initialize the connection to a file share

If you store the profile on a file share, try accessing the file share beforehand using Windows Explorer.

Check access rights

Firefox must also have the right to create files in the profile folder. The error can occur if you try to use a profile from a file system mounted with read-only permission (e.g. a remote Windows share which doesn't have "Allow network users to change my files" checked).

To check if the profile folder has the proper permissions:

1. Find your Firefox profile folder - see Finding your profile without opening Firefox.
   • If you only have one profile, its folder would have "default" in the name.
2. Right-click on your profile folder and select Properties.
3. Click on the General tab.

4.  Make sure Read-only is not checked marked.

Restore data from a locked profile

If you are unable to unlock the profile using the above methods, use the Profile Manager to create a new profile and migrate your data from the locked profile to the new profile. For information on how to do this, see Recovering important data from an old profile.

         Call +1-855-969-1880 for help and support of Mozilla Firefox not Responding.