Update: Still have the problems even after it updated the Firefox version to 64. Different version same annoying problems.

Sorry to hear about this problem.

If Firefox performed a Refresh, your old data should be in a folder on your desktop named Old Firefox Data -- do you see anything like that?

Please do not use the Windows "system restore" feature as that can blow away the Old Firefox Data folder.

If you have an Old Firefox Data folder:

Please double-click inside, then into the old profile folder (the name is partially random, like as34df56.default).

Can you find a file here named sessionstore.jsonlz4 ? That would be a file created when Firefox shut down normally. You can't read this file directly because it's compressed. To see whether it has the missing tabs, you can drag and drop it onto this page, then click Scrounge URLs: https://www.jeffersonscher.com/ffu/scrounger.html

That tool is on my site, so please let me know if it doesn't work for you.

If you can't find sessionstore.jsonlz4 or it doesn't have the right tabs, next step is to double-click into the sessionstore-backups folder.

The kinds of files you may find here are:

• recovery.jsonlz4: the windows and tabs in your live Firefox session at the time this folder was created
• recovery.baklz4: a backup copy of recovery.jsonlz4
• previous.jsonlz4: the windows and tabs in your last Firefox session
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update
• various .js files from Firefox 55 or earlier

Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs? You can use the Scrounger to examine promising candidates.

Any progress?

Hmm, how were you creating the backups you mentioned --

Yxxc12 said

...I can't restore any of the past backedup sessions from the past week!

-- were you backing up Firefox's session history files, or using an add-on?

I found the sessionstore folder, but it won't/couldn't drag & drop or copy & paste to the site. And when I try to browse for it it just opens the file. Am I supposed to select a certain file in the sessionstore folder like 1 of the "recovery" files? I do see files named those (previous.jsonlz4, recovery.baklz4, recovery.jsonlz4, ect except I don't see any various.js) in the folder. And half are dated(created & accessed) 12/12, the rest are dated a couple months earlier. I wasn't using an add-on, just clicked on the "Backup" under "import & backup" in "History" of Firefox.

My page can only read one file at a time, so try drag-and-drop with a single .jsonlz4 file.

(By various .js I meant various files with a .js extension. Those would be much older anyway.)

That's what I tried to do.

That can't be the only way to fix this.

Seriously.

You can try using the Browse button on the Scrounger page if drag-and-drop doesn't work for you. Hopefully you backed up the files to a convenient location so it's faster to load them.

I tried the site (drag & drop the file) again, & it said "Session history file contents could not be read?" after clicking Scrounge URLs.

Only files with a jsonlz4 file extension are useful.

Try to drag the most recent upgrade.jsonlz4-<build_id> file with a BuildId appended to the Scrounge website.