OK solved!
I have a post called “Cardio” with a child category name “Cardio”.
I created a category-cardio.php (cardio is the child category) but the page doesn’t display the post “cardio” same name as the category.
<?php
/**
* Cardio category template
*
* @package clf
*/
get_header(member);
?>
<div id="primary" class="content-area">
<main id="main" class="site-main">
<h1>category-cardio.php</h1>
<?php $args = array(
'categroy_name' => 'cardio',
) ?>
<?php $the_query = new WP_Query( $args ); ?>
<?php if ($the_query->have_posts()) : ?>
<?php while ($the_query->have_posts()) : $the_query->the_post();
echo the_content();
endwhile;
endif;
?>
</main><!-- #main -->
</div><!-- #primary -->
<?php
get_sidebar();
get_footer();