Orderering samples not working.

Customers can no longer place orders for samples / items that cost DKK 0. Only items that cost something. It works when i deactivate Woocommerce Pensopay. I have debugged and get the following message.

Uncaught Error: Call to undefined function wcs_order_contains_subscription() in /home/smartgar/public_html/wp-content/plugins/woo-pensopay/classes/woocommerce-pensopay-helper.php:53 Stack trace: #0 /home/smartgar/public_html/wp-includes/class-wp-hook.php(287): WC_PensoPay_Helper::order_needs_payment(false, Object(Automattic\WooCommerce\Admin\Overrides\Order), Array) #1 /home/smartgar/public_html/wp-includes/plugin.php(206): WP_Hook->apply_filters(false, Array) #2 /home/smartgar/public_html/wp-content/plugins/woocommerce/includes/class-wc-order.php(1499): apply_filters(‘woocommerce_ord…’, false, Object(Automattic\WooCommerce\Admin\Overrides\Order), Array) #3 /home/smartgar/public_html/wp-content/plugins/woocommerce/includes/admin/meta-boxes/class-wc-meta-box-order-data.php(247): WC_Order->needs_payment() #4 /home/smartgar/public_html/wp-admin/includes/template.php(1389): WC_Meta_Box_Order_Data::output(Object(WP_Post), Array) #5 /home/smartgar/public_html/wp-admin/edit-form-advanced.php(686): do_meta_boxes(Ob in /home/smartgar/public_html/wp-content/plugins/woo-pensopay/classes/woocommerce-pensopay-helper.php on line 53