Make sure that you do not run Firefox in permanent Private Browsing mode (Always use Private Browsing mode; Never Remember History).

• https://support.mozilla.org/kb/Private+Browsing

• Tools > Options > Privacy > Firefox will: "Use custom settings for history"
• Deselect: [ ] "Always use Private Browsing mode"

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button > Exit (Power button)
• Windows: File > Exit
• Mac: Firefox > Quit Firefox
• Linux: File > Quit

You can check for problems with the sessionstore.js file in the profile folder that stores session data. When sessionstore.js is deleted you lose pinned tabs and Tab Groups and open tabs and you will have to recreate them, so if necessary make a note or bookmark them.

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Unfortunately none of that worked. The "private browsing mode" was already unselected. Also, it used to warn me when I was closing multiple tabs and it doesn't do that anymore. I upgraded after all this started so I'm running the most recent version. The sessionstore.js is fine, I'd already checked that. Also, my three-bar menu doesn't work, either and I don't know if that's related or not.

Did you check "History > Recently Closed Tabs/Windows"?

Does Session Restore otherwise work and can you reopen closed tabs and windows?

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: "3-bar" menu button or Tools > Add-ons > Appearance
• Do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check for issues caused by plugins.

• set plugins to "Ask to Activate" on the about:addons page ("3-bar" menu button or Tools > Add-ons > Plugins)
• plugins are not affected by Firefox Safe Mode
• https://support.mozilla.org/kb/Troubleshooting+plugins

The "recently closed tabs" works but I didn't notice "restore all tabs". Doesn't matter. If I close the program and reopen it the "recently closed tabs" is grayed because it's a new session. So much for that.

i have had this happen TWICE when Firefox has crashed and all my tabs have crashed with it and history doesn't show squat and all these 'helpful' how-to's for people who aren't techie ONLY MAKE IT WORST. ok?!?!?! my preferences are set to restore, keep all my history - but when I have an update to my computer, BOOM - firefox acts like an abused child and runs and hides and takes my tabs and history with him!! there isn't anything you all have here that has worked, again, made it worst SO PLEASE ADMIT DEFEAT. THIS IS CRAP AND SUCH AN INCONVENIENCE TO LOSE ALL MY WORK!!!!!!!!!!!!!!!