To bookmark the current page, you can do any of these:

• Immediately bookmark the page in the Unsorted Bookmarks folder:
  • click the star icon on the toolbar (it is paired with the Bookmarks menu icon, which looks like a clipboard)

• Call up the Bookmark This Page dialog:
  • press Ctrl+Shift+d sorry: Ctrl+d
     
  • right-click the page > click the star icon
    Note: not available if you right-clicked a link, image, or form field
     
  • use the Bookmarks menu on the classic menu bar, which you can display using any of these:
    • Temporary display: tap the Alt key or press Alt+b
    • right-click a blank area of the tab bar > Menu Bar
    • right-click the "+" button on the tab bar > Menu Bar
    • "3-bar" menu button > Customize > Show/Hide Toolbars

You can also check for problems with the places.sqlite database file in the Firefox profile folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/