WC Hook element doesnt show up in the Email

We use the WC hook element to display the content of a third-party plugin in the new order email. It’s about the customer’s date of birth that matters. It worked without any problems until the last update. Now nothing is displayed in the e-mail. How can we get this information back in the email that we are asked for using the Checkout Fields Manager for WooCommerce plugin? We use the hook “woocommerce_email_after_order_table” for the query.