Menu gone; tags and categories no longer link to posts

We have a child site on a multi-site config running Catch Everest Pro (tcog.info). She has lost her menu. In Menu settings, the pages are no longer listed under the menu name. if you create a new menu or add pages to existing menu name, they do not save. Also, her blog posts no longer show the tags at the bottom. The Tags and Categories menu are visible with all the categories showing number of posts connected to them as well as the Tags. However, when you click on a Tag or Category, you receive "Nothing Found." The Search box does find posts. We have other Catch Theme sites on the network including others using Catch Everest Pro (njfog.org) and the menu works fine as well as posts. We went through all the plugins to check for conflicts; updated the theme, updated to latest version of WP. Finally, the Appearance > Customize page shows menu items on the left, but the web image never loads on the right; it just continuously spins. Are these connected and how to we fix this, primarily the menu issue? Thanks, Dan