Can you tell whether your Firefox performed a Refresh or created a new profile? To investigate:

(1) Old Firefox Data folder

In this process, your old profile folder containing extension data and custom data is moved to your desktop into an Old Firefox Data folder. Do you see anything like that?

(2) Profile Manager page

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!)

The profile that Firefox is currently using will have this:

This is the profile in use and it cannot be deleted.

Do you have any other profiles listed on this page? If so, you can check whether a profile is the one you were using recently by clicking its Launch profile in new browser button.

If it isn't what you want, simply close that new window.

If it IS what you want, back on the about:profiles page, click the Set as default profile button for that profile so Firefox uses it automatically at the next startup.

Anything useful there?

It was an usual ff update. Also, no new profile is created.

Hmm, the profile in the screenshot was created by a Refresh on or about August 3, 2021, so that was quite a while ago. I'm assuming your data loss was much more recent.

Did you lose any other extension data, or only OneTab?

Some reasons for extension data loss would be:

(1) Uninstall and reinstall of the extension

(2) Loss of the extensions.json data file

(3) Loss of the extension's folder under [profile folder]\storage\default

(4) Corruption of the extension's database file

I don't have a good solution for any of those, unfortunately. However, in #2, where an extension database is orphaned under an old extension UUID folder name, it sometimes is possible to find the old database and match it up with the new extension UUID folder name.

Yes, today only I have lost my data. I have lost the data for all my extensions. Can you please suggest anything