You need to assign the menu to the particular theme option from the admin end,
Orelse use this code,
wp_nav_menu( array( 'menu' => 'second-menu' ) );
Instead of,
wp_nav_menu( array( 'theme_location' => 'second-menu' ) );
This will work.
You need to assign the menu to the particular theme option from the admin end,
Orelse use this code,
wp_nav_menu( array( 'menu' => 'second-menu' ) );
Instead of,
wp_nav_menu( array( 'theme_location' => 'second-menu' ) );
This will work.