Sounds like a problem with the site definition. make sure the site is properly created for dynamic development:
http://www.webassist.com/tutorials/Define-a-dynamic-site-in-CS5
also make sure that you have a database connection set up:
http://www.webassist.com/tutorials/Create-a-PHP-database-connection
and make sure that you are using the PCMS add content to power CMS access point on a php page.
Power CMS cannot be added to a static html page.