Firefox has been my default browser since 2004. I have never had a problem with closing a Firefox session with 8-12 open tabs and then re-opening Firefox later and having all the same tabs re-open with the new Firefox session. But now, every time I close and then reopen a Firefox session, it is like I have installed a version update: no tabs are saved. I am not a programmer, I am not interested in looking for obscure files and performing digital surgery. I just want my tabs to open like they have for the last 18 years. In Settings under General my Open Previous Windows And Tabs checkbox is checked. Don't see anything else that is germane. My browser is up to date--latest version.