productdetails page not render joomla plugin

[Pirosoft]

Hi, i have plugin installed on my joomla (2.5.4) and virtuemart 2.0.4. Hi have tested a simple plugin in joomla article and go, but if i use in default.php page of produddetails tmpl not render the plugin.
Why? i enable the option "Enable Joomla Plugin" in option.