To check that the code is correctly installed on the website, you should change the following line in the link output code (which you insert on each page of the website)
<?php
$client = new BACKLINKS_client();
?>
to the line
<?php
$o = array();
$o['force_show_code'] = true;
$client = new BACKLINKS_client($o);
?>
If the commented number or <!--check code--> line does not appear in the page code, then the code is not installed correctly.