I've gone through all support pages, and still can't find a solution. I'm needing to restore to a specific day/time period. I lost literally hundreds of hours of research...and MUST find a way to get those Tab Groups and Tabs restored. Again, for some reason, the Restore Previous Session option is greyed out...and not an option. From what I've read, there may be some files in the Firefox profile folder that can be used, but it's not clear the steps to take to see if this would do what I need, and before I mess with those files, etc... I'd really need someone from tech support to review all this and assist me.