Try restoring the last session (Ctrl+Shift+T) and then recently closed windows (Ctrl+Shift+N).

I did with same result.

Can you go to your profile folder and then go into the folder sessionstore-backups. Post a screenshot of the files.

Thanks for your reply. Attached screenshot as requested.

Are you using Sync to sync the "Open tabs"?

• https://support.mozilla.org/en-US/kb/how-do-i-choose-what-types-information-sync-firefox

You can try to restore a recent upgrade.jsonlz4 file from the sessionstore-backups folder like from the last update. You can look at this tool to inspect a compressed jsonlz4 sessionstore file to see if i=t has the lost tabs. This tool works locally, no uploading done.

• https://www.jeffersonscher.com/res/scrounger.html

Thank you for these links. I have filed these away for the future.

After a few hours of rebuilding, I'm back to square one. I have an older PC that I run in parallel with my 2-month-old PC, so it was fairly straightforward to rebuild. Therefore, I don't want to do any restores at this point.

But I definitely will, should I run into this same issue.

Thanks again.