I always have two Firefox windows open: one for work, one for all the other stuff. The last two times I have restarted my computer (having closed Firefox before switching it off with a right click on the task bar icon and "close all windows"), only one of those windows has been restored. I didn't realise immediately either time, but when I clicked "recently closed windows" nothing happened, and there's no "restore previous session" option, either. I haven't been near my settings in months but I've checked and "startup" is indeed set to "open previous windows and tabs". I found an article here talking about troubleshooting options and went to about:support but the article said to click on "show folder" in the Application Basics table and all I can see is "open folder"... twice (update folder and profile folder), and I'm not knowledgeable enough to feel comfortable going further. Any help would be very welcome, thanks!