Have you checked your History settings and make sure that you didn't set it to "clear history when closed" or "Never Remember History"?

HKSim, thank you for your reply. Your right, I do have remove recent history. But, there are two options to retain history. #1 Remember browsing and download and #2 remember search and form history. Which would be better to use? Thank you.

Hi sciencemagic, the 2 options are for different things. 1) Browsing & Download History: Browsing history is the list of sites you've visited that are shown in the History menu, the Library window's History list and the address bar autocomplete list. Download history is the list of files you've downloaded that are shown in the Downloads window. 2) Form & Search History: Form history includes the items you've entered into web page forms for Form autocomplete. Search history includes items you've entered into the search field on the New Tab page or into Firefox's Search bar.

HKSim, thank you for your reply. Understand your comments. If I enable Browsing & Download History, will that slow my computer? My system is currently disabling all history. Thanks.

Hi sciencemagic, No, browsing and other history will not impact your computer performance. The actions of saving history is miniscule compared to even just opening and rendering a web page.