How to get Co-Author-Plus data via shortcode - wordpress

Question

with the following code I want to show the authors via the Co-Author-Plus plugin via shortcode using a php file. But this doesnt work. It just returns nothing. You know why?
Update code:
<?php function coauthorplus_function() {
ob_start();
$coauthors = get_coauthors();
$len = count( $coauthors );
if ( (function_exists( 'coauthors_posts_links' )) && ($len > 1) ) { ?>
<div class="authors-container">
<div class="author-image">
<?php echo get_avatar( $coauthor->user_email, '80'); ?>
</div>
<div class="author-data-details">
<div class="fdescription fdescriptions">Dieser Artikel wurde in Ko-Produktion durch folgende Autoren erstellt:</div>
<div class="authors-name">Von <?php coauthors_posts_links(); ?></div>
</div>
<div class="clearfix"></div>
</div>
<?php
} else {
global $post;
$author_id=$post->post_author;
foreach( get_coauthors() as $coauthor ):
?>
<div class="author-container">
<div class="author-image">
<?php echo get_avatar( $coauthor->user_email, '80'); ?>
</div>
<div class="author-data-details">
<div class="author-name">Von <?php coauthors_posts_links(); ?></div>
<div class="fdescription"> <?php echo $coauthor->description; ?></div>
</div>
<div class="clearfix"></div>
</div>
<?php endforeach;
}
return ob_get_clean(); } add_shortcode('coauthorplus', 'coauthorplus_function'); ?>
In my function.php which is on the same place in the webspace I included the following:
include('coauthorplus.php');