Hello,

Not sure what happened and what you have already tried, but please check out How to restore a browsing session from backup (I assume you've already read How do I restore my tabs from last time?)

If Firefox didn't shut down fully, it's possible you can recover the closed window here:

• "3-bar" menu button > History > Recently Closed Windows
• (menu bar) History > Recently Closed Windows
• Ctrl+Shift+N

If you see one of these, do this first:

• "3-bar" menu button > History > Restore Previous Session
• (menu bar) History > Restore Previous Session

Ctrl+Shift+N was life-saving. Nothing else worked. I will forever remember this advice! I'm so grateful

Thank you for reporting back. You might have a non-visible window which prevents Firefox from closing normally. You can try to find and close that using Firefox View. Either:

• click the file drawer icon at the left end of the tab bar
• type or paste about:firefoxview in the address bar and press Enter to load the page

Then in the left column, click Open Tabs to view your open tabs organized by window. You should be able to close any non-visible windows here.