Instead of adding the power gallery code to the PowerStore/Products detail page, you should add it to the long description when editing the product on the PowerStore/Admin/Products_Update.php page.
Log into the admin section of power store, then search for the product you wish to display the gallery for and click the edit button.
In the Long description field on the update page, change the HTML editor instance to code View and paste the PowerGallery Code. Then save your changes.