When the child page is defined to Word Press as a main page without a parent and the GP menu indicates the page is a child then the page does not get the “not found”
1 – set up the GP menu under Menus and select it in Customize
2 – set up the child page as a main page, without a parent
3 – in the Menus page indent the page under its parent and the menu will show it as a child and the page can be linked to
I still don’t have any idea if this is a GP or a WP issue ??