Primary Navigation not displaying correct navigation

Have you solved this since you posted? Thanks for the link.
I am confused about the exact problem, since the menus top and footer are obviously different. Are you using a cache plugin and haven’t cleared cache and seeing something different than I see?
Is it the order of items in the main menu? Is it just the ‘About’ section you don’t want there or do you want all items in this menu in a different order? The top and footer About sections are different. If so, in Appearance / Menus under Main Menu settings where it lists menu items, you can arrange the order they appear, add or delete whatever parts you want or don’t want to appear in Main Menu in each title’s drop arrow. Click the drop arrow to the right of About, there it will have Move Down or Remove. You can also drag each title to any order.

I implemented a fix to the symptom but not to the problem. I found that the site was displaying which every menu appeared first in the list of menus as the primary navigation. It was ignoring the primary navigation checkbox.

So I renamed the main menu to “1 – Main Menu” so that it appeared at the top of the list. This resolves the problem on the surface but not the actual underlying cause.

My apologies that you were seeing the menu after I figured out this fix.

Ah, thanks. Well, it appears to be a php prob with the menu calls between the upgrade and the theme functions with the walker nav. In wp includes nav-menu-template.php. / nav-menu.php. I am not versed in php, but saw this in nav-menu-template.php.

// get the first menu that has items if we still can't find a menu
	if ( ! $menu && !$args->theme_location ) {
		$menus = wp_get_nav_menus();
		foreach ( $menus as $menu_maybe ) {
			if ( $menu_items = wp_get_nav_menu_items( $menu_maybe->term_id, array( 'update_post_term_cache' => false ) ) ) {
				$menu = $menu_maybe;
				break;
			}

So that tells me something somewhere is not identifying the proper object.
This should point you in a direction. Someone else can help you. Or, you can also ask your theme support. Is there a theme update that may have addressed this? Sorry, I couldn’t do more for you.

This is very helpful, thank you.

The company that developed our theme went belly up.

I’ll dig in the direction you have pointed, thank you for taking the time to help.