CMB2 multiple files not displaying on page

<?php
/**
 * Get the bootstrap!
 */
if ( file_exists(  __DIR__ . '/cmb2/init.php' ) ) {
  require_once  __DIR__ . '/cmb2/init.php';
} elseif ( file_exists(  __DIR__ . '/CMB2/init.php' ) ) {
  require_once  __DIR__ . '/CMB2/init.php';
}

add_action( 'cmb2_admin_init', 'cmb2_metaboxes' );
/**
 * Define the metabox and field configurations.
 */
function cmb2_metaboxes() {

  // Start with an underscore to hide fields from custom fields list
  $prefix = '_cubo_';

  /**
   * Initiate the metabox
   */
  $cmb = new_cmb2_box( array(
      'id'            => 'cubo_metabox',
      'title'         => __( 'Project', 'cmb2' ),
      'object_types'  => array( 'projects' ), // Post type
      'context'       => 'normal',
      'priority'      => 'high',
      'show_names'    => true, // Show field names on the left
      // 'cmb_styles' => false, // false to disable the CMB stylesheet
      // 'closed'     => true, // Keep the metabox closed by default
  ) );

  $cmb->add_field( array(
      'name'         => __( 'Images', 'cmb2' ),
      'desc'         => __( 'Upload project images.', 'cmb2' ),
      'id'           => $prefix . 'file_list',
      'type'         => 'file_list',
      'preview_size' => array( 150, 150 ), // Default: array( 50, 50 )
  ) );

}
 ?>

<?php
/**
* Sample template tag function for outputting a cmb2 file_list
*
* @param  string  $file_list_meta_key The field meta key. ('wiki_test_file_list')
* @param  string  $img_size           Size of image to show
*/
function cmb2_output_file_list( $file_list_meta_key, $img_size = 'medium' ) {

  // Get the list of files
  $files = get_post_meta( get_the_ID(), $file_list_meta_key, 1 );

  echo '<div class="file-list-wrap">';
  // Loop through them and output an image
  foreach ( (array) $files as $attachment_id => $attachment_url ) {
      echo '<div class="file-list-image">';
      echo wp_get_attachment_image( $attachment_id, $img_size );
      echo '</div>';
  }
  echo '</div>';
}
 ?>

<?php
get_header(); ?>

    <div id="primary" class="content-area">
        <main id="main" class="site-main" role="main">
        <?php
        while (have_posts()) : the_post();

            get_template_part('template-parts/content', 'projects', get_post_format());

            // // If comments are open or we have at least one comment, load up the comment template.
            // if (comments_open() || get_comments_number()) :
            //     comments_template();
            // endif;

                        cmb2_output_file_list( 'cubo_metabox', 'small' );


        endwhile; // End of the loop.

        ?>

        </main><!-- #main -->
    </div><!-- #primary -->
 ?>

<div class="file-list-wrap"><div class="file-list-image"></div></div>

  70    _cubo_file_list     a:7:{i:73;s:54:"http://cubo.dk/wp-content/uploads/2016/08/dta_2x-6.jpg";i:78;s:54:"http://cubo.dk/wp-content/uploads/2016/08/dta_2x-1.jpg";i:77;s:54:"http://cubo.dk/wp-content/uploads/2016/08/dta_2x-2.jpg";i:76;s:54:"http://cubo.dk/wp-content/uploads/2016/08/dta_2x-3.jpg";i:74;s:54:"http://cubo.dk/wp-content/uploads/2016/08/dta_2x-5.jpg";i:75;s:54:"http://cubo.dk/wp-content/uploads/2016/08/dta_2x-4.jpg";i:72;s:52:"http://cubo.dk/wp-content/uploads/2016/08/dta_2x.jpg";}