Emails from 3rd party plugin will not send.

Hello!

We have implemented a building using Pre-Orders Pro from Bright Themes. We have gone through the development steps for adding the email ID’s to our child theme, however, the emails for the pre-orders still do not send. We can see the email types for pre-orders and make templates for them within WooCommerce Email Template Customizer Premium, and if we disable the plugin, the pre-order emails will send perfectly. When the plugin is active we can see that they don’t even attempt to send using WP Mail SMTP. Any help would be hugely appreciated.

Thanks