Pagination stops at page 2

Hi,

I’m experiencing a rather annoying issue and could do with some help.

I’ve got a static homepage that displays my latest custom post types (two in total).
The problem is that pagination seems to stop dead at page 2, even though there should be 4 pages in total.

Here’s the code from my homepage template:

<?php get_header(); ?>

    <div id="masonry" class="row">

        <?php if ( get_query_var('paged') ) {
            $paged = get_query_var('paged');
        } elseif ( get_query_var('page') ) {
            $paged = get_query_var('page');
        } else {
            $paged = 1;
        }?>

        <?php $post_args = array( 'post_type' => array( 'sound', 'web' ), 'posts_per_page' => 9, 'paged' => ( get_query_var('page') ? get_query_var('page') : 1 ) ); ?>
        <?php $loop = new WP_Query( $post_args ); while ( $loop->have_posts() ) : $loop->the_post(); ?>

            <div class="col-xs-12 col-sm-4 item">
                <div class="inner">
                    <a href="<?php the_permalink(); ?>"><img src="<?php the_field('work_thumb'); ?>" alt="Jase Warner – <?php the_title(); ?>" /></a>
                    <a href="<?php the_permalink(); ?>" class="overlay"><span class="title"><span class="wrap"><?php the_title(); ?></span></span><span class="tagline"><?php the_field('work_tagline'); ?></span></a>
                </div>
                <div class="hidden-md hidden-lg">
                    <a href="<?php the_permalink(); ?>" class="sm-title"><?php the_title(); ?></a>
                    <p class="sm-tagline"><?php the_field('work_tagline'); ?></p>
                </div>
            </div>

        <?php endwhile; wp_reset_query(); ?>

    </div>

    <div id="load-more">
        <?php next_posts_link( 'Load More', $loop->max_num_pages > 1 ); ?>
    </div>

<?php get_footer(); ?>

I should mention that I’m using infinitescroll.js with this, though I don’t think that’s to blame for the issue.

Here’s a link to the page where the problem exists: http://217.199.187.196/jw-staging.com/

Any help would be greatly appreciated!