I use Firefox every day and have since the browser's very early days. I have a Firefox account, and am logged in when using it. Typically, I have some pinned tabs (calendar, for instance) and also some tab groups (Container Tabs). There are usually a small number of open tabs. For example, this week, I have been googling spreadsheet formulas for a Google Sheet I am working on. Occasionally, perhaps once every couple of months. when I open the browser, everything is gone. All the pinned tabs, tab groups, and the tabs I'd left open deliberately are not there. Just one tab (Google), is open. I can re-open the container tabs and add them to the tab bar again, try and remember which tabs were pinned and redo those, but having to trawl through history to find the very detailed searches for spreadsheet formulas and work-rounds - is all very tedious and shouldn't be happening! It has only been happening for at most a year, maybe seven or eight times in total, but those seven or eight times shouldn't happen. I have searched for a way to restore it to how it was the last time I closed it, but cannot find any way to restore Firefox to how it had been. I am using an a fairly new ASUS laptop (but it happened on my previous PC too), with Windows 11 installed and up-to-date. Firefox is always kept up-to-date too. Any suggestions would be very welcome.