It was 99% the same code. I found the 1%.
The site that worked used:
<?php wp_nav_menu( array(‘menu’ => ‘Main Menu’ )); ?>
The site that didn’t work used:
<?php wp_nav_menu( array(‘menu’ => ‘Primary Menu’ )); ?>
“Main Menu” is what I have in the Menu Name field in Appearance > Menus, and “Primary Menu” is the theme location of the menu. In the older version of WP (still active on my live site so I just verified this), using the theme location in the function worked fine. In WP 4.0, it looks like only the Menu Name works in the function. Since it couldn’t find a menu called “Primary Menu,” it chose the first menu in my list alphabetically.
Happily resolved! Thanks for the guidance ??
this was the problem exactly for me. deleted a (unused) menu that came before Primary alphabetically so that my Primary menu appeared.