Images appear in the header on all pages, but not category.php

Good morning!

So this sounds like unbalanced html tags…

And indeed, if I concatenate your header file with your category.php file, there are a few closing and a closing tags at the end that don’t seem to belong there…

I’d suggest a good tag cleanup: make sure everything you open is closed, and you don’t have any orphaned closing tags.

Also, but I doubt this relates to your problem here, your logo in the header.php file has an extra backslash:

echo '<a href="'.  get_bloginfo('wpurl') . '"><img src="' . $image[0] . '" / /></a>';

It should be

echo '<a href="'.  get_bloginfo('wpurl') . '"><img src="' . $image[0] . '" /></a>';

UPDATE

Wait, ok, so you added the whole loop at the top for cover-story posts? If that’s the case, then you want to call wp_reset_postdata after your loop, otherwise you have affected the normal page’s current, main loop. You should also check and only reset the loop if you actually had posts to show. Changing that top part, then, it becomes: (new lines indicated)

<?php
    $cat_id = get_query_var('cat');
    $args = array( 'post_type' => 'cover-story', 'posts_per_page' => 1, 'orderby' => 'menu_order', 'order' => 'ASC', 'cat' => $cat_id );
    $loop = new WP_Query( $args );
    if ( $loop->have_posts() ) { // <-------------
        while ( $loop->have_posts() ) : $loop->the_post();
            $attachment_id = get_post_thumbnail_id( $post->ID);
            $img_src = wp_get_attachment_image_url( $attachment_id, 'full' );
            $img_srcset = wp_get_attachment_image_srcset( $attachment_id, 'full' );
?>
<img class="featured-story tablet-only" src="https://wordpress.stackexchange.com/questions/255434/<?php echo esc_url( $img_src ); ?>"
    srcset="https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/<?php echo esc_attr( $img_srcset ); ?>"
    sizes="(max-width: 50em) 87vw, 680px">
<img class="featured-story mobile-only" src="https://wordpress.stackexchange.com/questions/255434/<?php echo esc_url( $img_src ); ?>"
    srcset="https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/<?php echo esc_attr( $img_srcset ); ?>"
    sizes="(max-width: 50em) 87vw, 680px">
<div class="cover-story-text mobile-only">
    <p>
    Cover Story
    </p>
    <h2><?php the_title(); ?></h2>
    <a href="<?php the_permalink(); ?>">Read More</a>
</div>
<div class="featured-story desktop-only" style="background: url(<?php the_post_thumbnail_url( 'full' ); ?>);">
    <div class="cover-story-text">
        <p>
          Cover Story
        </p>
        <h2><?php the_title(); ?></h2>
        <a href="<?php the_permalink(); ?>">Read More</a>
    </div>
</div>

<?php
        endwhile;
        wp_reset_postdata(); // <-------------
    endif; // <-------------
?>

Hope this helps!