Just figured this out, for anyone else may encounter the same issue.
You can add the following to the functions file of your child theme:
function special_nav_class ($classes, $item) {
if (in_array('current-menu-item', $classes) ){
$classes[] = 'highlight-active-page';
}
return $classes;
}
add_filter('nav_menu_css_class' , 'special_nav_class' , 10 , 2);
In my case I created a class called: ‘highlight-active-page’ as seen above. So make sure to name and add accordingly for your needs.
My solution did not straight away work due to the vagaries of my WordPress configuration with Pagelines Platform 5 so you may need to do some extra leg work, like I did to get it working.