Older / Newer Posts link not working

I am trying to figure out why on the main page of the blog, the /older posts page takes me to a new page, but it has the same posts as the main page. These links work for the category specific blogs or if you are on a single post… but not the main page. Can someone help me out? I have tried several threads here on this site for help and haven’t found a solution yet.

the website is: https://www.atlaserlights.com/blog

the code on the index.php file reads:

https://pastebin.com/mgfaxFhb

<?php get_header(); ?>

                <div id="primary">
                        <div id="content" role="main">

                        <?php query_posts($post_string . '&cat=-5'); ?>
                        <?php if ( have_posts() ) : ?>

                                <?php twentyeleven_content_nav( 'nav-above' ); ?>

                                <?php /* Start the Loop */ ?>
                                <?php while ( have_posts() ) : the_post(); ?>

                                        <?php get_template_part( 'content', get_post_format() ); ?>

                                <?php endwhile; ?>

                                <?php twentyeleven_content_nav( 'nav-below' ); ?>

                        <?php else : ?>

                                <article id="post-0" class="post no-results not-found">
                                        <header class="entry-header">
                                                <h1 class="entry-title"><?php _e( 'Nothing Found', 'twentyeleven' ); ?></h1>
                                        </header><!-- .entry-header -->

                                        <div class="entry-content">
                                                <p><?php _e( 'Apologies, but no results were found for the requested archive. Perhaps searching will help find a related post.', 'twentyeleven' ); ?></p>
                                                <?php get_search_form(); ?>
                                        </div><!-- .entry-content -->
                                </article><!-- #post-0 -->

                        <?php endif; ?>

                        </div><!-- #content -->
                </div><!-- #primary -->

<?php get_sidebar(); ?>
<?php get_footer(); ?>