show billing_vat

Hello.
I have your plugin and the premiun templates. ( i use the bussisnes template)
I would like to know how I can show below the name of the client “billing_vat”
I tested this code but does not work me.

add_action( ‘wpo_wcpdf_after_order_data’, ‘wpo_wcpdf_billing_vat’, 10, 2 );
function wpo_wcpdf_billing_nif ($template_type, $order) {
global $wpo_wcpdf;
?>
<tr class=”billing-vat”>
<th>NIF:</th>
<td><?php $wpo_wcpdf->custom_field(‘billing_vat’); ?></td>
</tr>
<?php
}

Can you help me?

Thank you

https://ww.wp.xz.cn/plugins/woocommerce-pdf-invoices-packing-slips/