Custom Post Type Archive Not Showing Posts

I generally include this chunk of code with my custom post types:

// Load the custom post type archive page template
add_filter( 'archive_template', 'posttype_archive_template' ) ;
function posttype_archive_template( $archive_template ) {
  global $post;
  if ( is_post_type_archive ( 'posttype' ) ) {
    if(file_exists(PLUGIN_PATH. '/archive-posttype.php'))
       $archive_template = PLUGIN_PATH. '/archive-posttype.php';
  }
  return $archive_template;
}