Pagination reloads first page but has proper url

Question

So I built a blog for someone but I'm having an issue with the homepage. The homepage is set to show 9 posts before the pagination turns on (set in WP admin settings), but when you click on page 2, 3 or any number, it shows the same content as page 1 (note that the url will display the right /page/#) but it always shows the first 9 latest posts and still has page one selected in the pagination.

In my WP settings I have the front page display set to "your latest posts" and in my index.php being used as the homepage, I'm simply calling the loop and pagination:

<?php get_template_part('loop'); ?>
<?php get_template_part('pagination'); ?>

Using that code in my category templates works perfectly as the pagination functions right and always shows the right posts per page.

I've seen similar questions posted, but in those cases they're using custom queries.

The loop (same for the categories with working pagination):

<?php if (have_posts()): while (have_posts()) : the_post(); ?>

    <!-- article -->
    <article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>

        <!-- post details -->
        <span class="loop_cat"><?php the_category(' '); ?></span>
        <span class="date"><?php the_time('Y.m.d'); ?></span>

        <!-- post thumbnail -->
        <?php if ( has_post_thumbnail()) : // Check if thumbnail exists ?>
            <a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
                <?php the_post_thumbnail('full'); // Declare pixel size you need inside the array ?>
            </a>
        <?php endif; ?>
        <!-- /post thumbnail -->

        <?php echo do_shortcode('[Sassy_Social_Share]'); ?>

        <!-- post title -->
        <h3>
            <a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a>
        </h3>
        <!-- /post title -->

        <a href="<?php get_custom_field('buy-link', TRUE); ?>" target="_blank"><h4 title="Purchase"><?php get_custom_field('price', TRUE); ?></h4></a>

        <div class="divider_excerpt"></div>

        <?php html5wp_excerpt('html5wp_index'); // Build your custom callback length in functions.php ?>

        <!-- <?php edit_post_link(); ?> -->

    </article>
    <!-- /article -->

<?php endwhile; ?>

<?php else: ?>

    <!-- article -->
    <article>
        <h2><?php _e( 'Sorry, nothing to display.', 'html5blank' ); ?></h2>
    </article>
    <!-- /article -->

<?php endif; ?>

EDIT:

<!-- pagination -->
<div class="pagination">
    <?php html5wp_pagination(); ?>
</div>
<!-- /pagination -->

EDIT:

Turns out this line of code I had right above the rest to exclude a specific category from the homepage loop is what caused the issue:

 <?php if (is_home()) {
   WP_Query("cat=-4")
 ;} ?>

Answer 1

Turns out this line of code I had right above the rest to exclude a specific category from the homepage loop is what caused the issue:

    <?php if (is_home()) {
      WP_Query("cat=-4")
    ;} ?>