This has been an issue that I've been having for the past month and have been unable to find a proper fix to it. While Firefox opens normally, none of the previous windows show up on screen. Even though I can still technically interact such as opening new tabs in it and click through tabs with Firefox View. Once I try to pull them up none of them show on the monitor nor can be interacted with further. I have both uninstall and reinstall Firefox and deleted/rename the xulstore.json, but neither of them fix the problem The only temporary solution I've found is through refreshing Firefox through about:support, even then it only takes a couple days to suddenly have the problem come back all over again. For added info I'm using a 2019 iMac with 15.2 OS.