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Customize > menu > primary > link > title attribute for the primary menu. When I mouse over the links in the primary menu (in process or published), I only see a repeat of the link name, not the title attribute. Social and footer menus work as expected to show the title attribute when links are moused-over. Thank you

This is exactly what just happened for me. A year ago 'Customize' was working fine. I just upgraded to WP 5.0.2, and now my Customize page shows only the option 'Widget' and nothing else. I did backup before I updated, and I updated my 10 or so plugins before I updated Word Press. I did NOT update my theme, because of the warning that any changes to the theme would be lost. My theme is noted as HAVEN (at a glance), but does not show under 'Customize.'  Help?