Hi, thanks for reaching our support!!

As, there is no default setting to add required field, so you have to do a bit of custom coding using this actions to apply the required condition :

add_action('woocommerce_single_product_summary', array($WC_Woocommerce_Catalog_Enquiry->frontend,'add_form_for_enquiry_without_popup'),100);

add_action('woocommerce_single_product_summary', array($WC_Woocommerce_Catalog_Enquiry->frontend,'add_form_for_enquiry'),100);