Any session history file from July is probably obsolete now, but generally speaking, Firefox will check at startup for:

(1) sessionstore.jsonlz4 at the main level of the profile folder

(2) if #1 isn't found, Firefox will look in the sessionstore-backups folder and try recovery.jsonlz4 or recovery.baklz4

(3) I don't know when/if Firefox will try previous.jsonlz4 or the files from recent updates

With that in mind, it often works best to try to substitute an earlier file for the latest one, assuming that won't cause more data loss than it cures.

This is an old set of steps. I have not retested lately:

(1) From inside Firefox, open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Open Folder" button. This should launch a Windows File Explorer window listing the various files and folders in your profile.

(2) Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button Exit
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup -- a file named sessionstore.jsonlz4 should appear in the folder.

(3) Once Firefox has stopped updating things, while viewing the main level of the profile folder, right-click > Rename sessionstore.jsonlz4 to sessionstoreOLD.jsonlz4

If you see an older sessionstore.js or sessionstore.bak file, move it somewhere else or delete it.

(4) Copy in the other file you want to restore, and rename it with the name appropriate for its format:

• Compressed file such as recovery.jsonlz4 => sessionstore.jsonlz4
• Uncompressed file such as recovery.js => sessionstore.js

(5) Start Firefox and it should read the swapped in sessionstore file and restore whatever was in the substitute file; if you do not have Firefox set to restore your previous windows and tabs automatically, use History > Restore Previous Session

Any luck?

It worked! Why this time I'm not sure. I kept the old json file from July and that one worked today finally too.

I just deleted everything in session backup file and the standalone sessionstore file then pasted the old file in both places and it worked. I thought I did this last time but never got anywhere.

And the restore window for today's issue worked great. Thank you. Got everything back