In Pronamic Pay version 8 we have removed support for WP eCommerce. The creators of the WP eCommerce plugin seem to have given up on the plugin. And that is also understandable with the enormous growth of WooCommerce. The WP eCommerce integration has therefore been permanently removed in Pronamic Pay version 8. If you still use WP eCommerce, now is the time to switch to WooCommerce.