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have downloaded4.0.1 three times and yet it's not running??

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  • Last reply by Svetlana
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I keep receiving the warning that I need to upgrade to 4.0.1. I have done so 3 times already. Why is it not working?

I keep receiving the warning that I need to upgrade to 4.0.1. I have done so 3 times already. Why is it not working?

All Replies (1)

  1. Exit Firefox (File>Quit) and check that no firefox.exe processes are running in task manager (ctrl+alt+del, processes tab). Try starting Firefox again and checking for the issue.
  2. If that doesn't work, please try to do a manual install. installing firefox