Add Invoice PDF URL to Order Meta

Previously this was covered in this post: https://wordpress.org/support/topic/orders-rest-api-pdf-link/

However, the code provided below doesn’t seem to be working any longer. Is it possible to provide some updated code? Thank you so much!

add_action( 'wpo_wcpdf_before_document', function( $document_type, $order ) {
	if( !empty($order) && $document_type == 'invoice' ) {
		$debug_settings = get_option('wpo_wcpdf_settings_debug', array());
		if( isset($debug_settings['guest_access']) ) {
			$pdf_url = admin_url( 'admin-ajax.php?action=generate_wpo_wcpdf&template_type=".$document_type."&order_ids=" . $order->get_id() . "&order_key=' . $order->get_order_key() );
			update_post_meta( $order->get_id(), '_wcpdf_document_link', esc_attr($pdf_url) );
		}
	}
}, 10, 2 );