This is what activates the cron:
Check e-mail. Make sure you have those 2 plugins which were included in the product
PHP Code:
<plugins>
<plugin active="1" executionorder="6">
<title>Initialize front-end vBMS page elements</title>
<hookname>global_start</hookname>
<phpcode><![CDATA[require_once(DIR . "/includes/vbms_frontend_init.php");]]></phpcode>
</plugin>
<plugin active="1" executionorder="5">
<title>Check e-mail</title>
<hookname>parse_templates</hookname>
<phpcode><![CDATA[require_once(DIR . "/includes/vbms_functions.php");
$cronimage .= vbms_get_check_mail_img_html();]]></phpcode>
</plugin>
</plugins>
Do a view source on any forum page and towards the end of the page see if you have that line