Only one post is showing on category page, why?

It’s pretty easy to see why your code shows only one post – there is no loop in your template file, so why should it show more posts than one?

To be honest… It looks more like single post template and not like category archive…

This should work a little bit better (or at least it should show more posts):

<?php
get_header(); 
/**
 * The template for displaying Category pages
 */
quality_breadcrumbs();
?>

<section id="section-block" class="site-content">
    <div class="container">
        <div class="row">
        <!--Blog Posts-->
        <?php echo '<div class="col-md-'.( !is_active_sidebar( "sidebar-primary" ) ?"12" :"8" ).' col-xs-12">'; ?>
            <?php while ( have_posts() ) : the_post(); ?>
            <article class="cat-post">  
                <figure class="cat-figure">
                    <?php $defalt_arg =array('class' => "img-responsive"); ?>
                    <?php if(has_post_thumbnail()): ?>
                    <a  href="https://wordpress.stackexchange.com/questions/320316/<?php the_permalink(); ?>">
                        <?php the_post_thumbnail($defalt_arg); ?>
                    </a>
                    <?php endif; ?> 
                </figure>

                <div>    
                    <?php if($current_options['home_meta_section_settings'] == '' ) {?>

                    <?php } ?>

                    <header class="entry-header">
                        <h2 class="entry-title"><a href="https://wordpress.stackexchange.com/questions/320316/<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
                    </header>   

                    <div class="entry-content">
                        <?php the_excerpt(__('Read More','quality')); ?>

                        <?php if($current_options['home_meta_section_settings'] == '' ) { ?>     

                        <span class="entry-meta">
                            <?php $cat_list = get_the_category_list();
                                if(!empty($cat_list)) {
                            ?>

                            <span class="author-image"> <?php echo ' ';?><a href="<?php echo get_author_posts_url( get_the_author_meta( 'ID' ) );?>"><?php echo get_the_author();?></a> |</span><span class="cat-links"><?php _e('','quality');?><a href="https://wordpress.stackexchange.com/questions/320316/<?php the_permalink(); ?>"><?php the_category(' '); ?></a></span> |  <a class="entry-date" href="<?php echo get_month_link(get_post_time('Y'),get_post_time('m')); ?>"> <?php echo get_the_date('M j, Y'); ?></a>
                            <?php } ?>
                        </span>
                    <?php } ?>
                </div>
            </article>    
            <?php endwhile; ?>          

            <?php wp_link_pages();?>    
            <!--/Blog Content-->
            <?php comments_template('',true); ?>
        </div>
        <?php get_sidebar(); ?>
    </div>
</section>
<?php get_footer(); ?>