Fatal error: Call to undefined method WPO_WCPDF_Receipt_Document::number()

Hello, i have this error when i click to a receipt (or invoice) into the Woocommerce orders page:

Fatal error: Call to undefined method WPO_WCPDF_Receipt_Document::number()
/home/customer/www/mitochon.it/public_html/wp-content/plugins/woocommerce-pdf-ips-templates/templates/Simple Premium/receipt.php (68) 0 /home/customer/www/mitochon.it/public_html/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/documents/abstract-wcpdf-order-document.php(1106): include() 1 /home/customer/www/mitochon.it/public_html/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/documents/abstract-wcpdf-order-document.php(950): WPO\WC\PDF_Invoices\Documents\Order_Document->render_template(‘/home/customer/…’, Array) 2 /home/customer/www/mitochon.it/public_html/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/documents/abstract-wcpdf-order-document.php(905): WPO\WC\PDF_Invoices\Documents\Order_Document->get_html() 3 /home/customer/www/mitochon.it/public_html/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/documents/abstract-wcpdf-order-document.php(972): WPO\WC\PDF_Invoices\Documents\Order_Document->get_pdf() 4 /home/customer/www/mitochon.it/public_html/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/class-wcpdf-main.php(519): WPO\WC\PDF_Invoices\Documents\Order_Document->output_pdf(‘inline’) 5 /home/customer/www/mitochon.it/public_html/wp-includes/class-wp-hook.php(324): WPO\WC\PDF_Invoices\Main->generate_document_ajax(”) 6 /home/customer/www/mitochon.it/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(”, Array) 7 /home/customer/www/mitochon.it/public_html/wp-includes/plugin.php(517): WP_Hook->do_action(Array) 8 /home/customer/www/mitochon.it/public_html/wp-admin/admin-ajax.php(188): do_action(‘wp_ajax_generat…’) 9 {main}

Can you help me please?
Regards
Alberto

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