You say that you've 'updated' Firefox but have you tried 'refreshing it'?
(Hamburger > Help > Troubleshooting Information > Refresh Firefox. You bookmarks will be retained but you'll need to reinstall a certain extension afterwards).
If refreshing doesn't work, try uninstalling Firefox and then, after restarting your computer, reinstalling it. (NB: It seems that a fresh installation of Firefox usually retains your old profile but I wouldn't trust it to always do so. Therefore you should export your bookmarks file first, so that you've got it available to import back again if the need arises. To do so, press Ctrl+Shift+B, click Import & Backup, select Export Bookmarks to HTML, choose a suitable location and save your file. If you need to import the file back again later, the process is much the same but simply choosing 'Import' instead of 'Export')