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FF stopped opening a window when run. The window shows in the rollover of the FF icon in Widows 10. Reinsalled FF after uninstalling other recents installs.

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When I run FF, an icon appears in a Windows 10 toolbar. However, no window opens. When I mouse over the icon, I see the usual small version of the window with default URL, but clicking on it still does not open a window. I've tried uninstalling all the software for a recently installed printer and reinstalling FF. No good. What next?

When I run FF, an icon appears in a Windows 10 toolbar. However, no window opens. When I mouse over the icon, I see the usual small version of the window with default URL, but clicking on it still does not open a window. I've tried uninstalling all the software for a recently installed printer and reinstalling FF. No good. What next?

Chosen solution

For additional context and commentary, try this older thread: https://support.mozilla.org/questions/1149793

Speaking of "older" -- your Firefox identified itself to the forum as version 49. Oh wait, it's SeaMonkey. Hmm... not sure why it is detected as Firefox 49 but I'll leave that question for SeaMonkey support people wherever they may be.

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https://support.mozilla.org/en-US/kb/changes-toolbars-and-window-sizes-are-not-saved You may have corrupt xulstore.json or Localstore.rdf file.

Close Firefox. Open your file browser to this hidden location:

  • Mac:’’' *~/Library/Application Support/Firefox/
  • Linux:’’' *~/.mozilla/firefox/
  • Windows:’’' %AppData%\Mozilla\Firefox\
  • *C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\

Locate the above files. Then rename or delete them. Restart Firefox.

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Chosen Solution

For additional context and commentary, try this older thread: https://support.mozilla.org/questions/1149793

Speaking of "older" -- your Firefox identified itself to the forum as version 49. Oh wait, it's SeaMonkey. Hmm... not sure why it is detected as Firefox 49 but I'll leave that question for SeaMonkey support people wherever they may be.

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Thank you. It would not have occurred to me that a nonexistent second monitor had mysteriously been activated and FF was displayed on it. I truly appreciate what you both do. I really expected to wait a week for a useless reply.