[Plugin: pbd-ajax-load-posts] doesn't work in my own theme

“I developed my own” completely stripped (naked/blank how you want to call it :P) theme for wordpress but during that process I deleted something that now is causing me troubles with a plugin that i am using.

I found this amazing plugin/tutorial online:
https://www.problogdesign.com/wordpress/load-next-wordpress-posts-with-ajax/

instead of next or previous post links it generates a button that loads more posts on the same page (like twitter and Facebook do for example)

It works perfect in the standard WordPress themes (TwentyTen, TwentyEleven ect.) but when I change to my own theme the functionality stops working. I can press the button but the next posts are not showing. (The functionality itself still works because it mentions at the good moment that there are no more posts). I use the #content and .navigation as mentioned in the plugin

I found out that it’s a piece of code in the loop.php script from the original WordPress themes that I should use in my own theme too but I can’t find what it is exactly…

This is my code in the index.php at the moment:

<?php get_header(); ?>

<?php while ( have_posts() ) : the_post(); ?>
<div class="article">

<?php if(get_post_meta(get_the_ID(), "_related-video", true) != ''){
 echo get_post_meta(get_the_ID(), "_related-video", true);
}else{
 the_post_thumbnail( 'main' );
} ?>

<h1><?php the_title(); ?></h1>
<i><?php the_date(); ?></i><br/>
 <?php the_tags('<h2>#', '</h2> <h2>#', '</h2>'); ?><br/>

<p>
<?php the_content(); ?>
<?php wp_link_pages(array('before' => 'Pages: ', 'next_or_number' => 'number')); ?>
</p>

</div>

<?php endwhile; ?>

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

I hope someone can help me,
Thank you in advanced for your time!