When I restarted Firefox all my bookmarks were gone and I can't save any new ones

Hi Francine, I'm sorry to hear about this problem. If you cannot save any new bookmarks, that can indicate that the Places database file which stores bookmarks and history was locked so Firefox start up with bookmark-features broken. You might need to restart your Mac to resolve that, or maybe just quitting and restarting Firefox will help. As for not having your bookmarks, could you try the steps in the following article: [[Recover lost or missing Bookmarks]].