Hi Tammy,
This usually happens because mobile menus are often controlled separately from desktop layouts in WordPress themes. Even if Conditional Headers are set correctly, the theme’s responsive CSS or mobile menu script may still be loading the Main Menu on smaller screens.
A good approach is to check your theme’s “Mobile Menu” settings first (Appearance → Customize → Header/Menus). If there is no option there, you can hide the Main Menu on mobile using a simple CSS media query targeting mobile breakpoints (e.g. display: none; for the main menu class under 768px width).
Also, make sure no caching plugin or header builder override is reintroducing the menu on mobile view.
Hope this helps you fully remove the Main Menu on mobile while keeping the Secondary Menu intact 👍
