Windows – “Thunderbird is already running” error every time I try to start Thunderbird, even if it is not running


I cannot open Thunderbird. The process isn't running, but when I click on the icon, I get the the following error:

Thunderbird is already running, but is not responding. To open a new window, you must first close the existing Thunderbird process, or restart your system.

I've tried the following:

  • Ending the task in Task Manager
  • Deleting parent.lock
  • Uninstalling Thunderbird
  • Uninstalling Firefox
  • Running Thunderbird in software "safe mode" and Windows safe mode

What can I do to fix this problem?

The problem looks more serious than expected. I do not see any Mail folder in my profile at C:\Users\your-username\AppData\Mozilla\Thunderbird. I think I lost my email.

Best Answer

You said you've tried ending the task in task manager, but have you tried ending the process in the task manager?

Does it ever work correctly, for example the first time after rebooting your computer?

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