[Plugin: Attachment File Icons (AF Icons)] icons for custom template

Hi there,
this plugin does exactly what i need, in theory. however, i’m having trouble getting the icons to show up in this custom theme i built for a catalog website. i’m still just getting a blank placeholder icon instead of the ones available in the plugin settings.
is there something i need to add or change here to make it work?

the following code is that i am using to display the attachments in my single.php template:

<h3><div class="attachments"><dl class="attachments attachments-small"><?php
$args = array( 'post_type' => 'attachment', 'numberposts' => -1, 'post_mime_type' => 'application/pdf, application/x-pdf, application/acrobat, applications/vnd.pdf, text/pdf, text/x-pdf, application/acad, application/x-acad, application/autocad_dwg, image/x-dwg, application/dwg, application/x-dwg, application/x-autocad, image/vnd.dwg, drawing/dwg, application/octet-stream', 'post_status' => null, 'post_parent' => $post->ID );
$attachments = get_posts($args);
if ($attachments) {
	foreach ( $attachments as $attachment ) {
	?>	<dt class="icon"> <?php echo get_attachment_icon($attachment->ID); ?></dt> <dd class="caption"> <?php echo the_attachment_link( $attachment->ID , false );
	}
}
?></dd></dl></div></h3>

thank you for your assistance!

https://www.ads-software.com/extend/plugins/attachment-file-icons/