Fast Secure Contact form does not work anymore with WP-Mail-SMTP

I always used this plugin together with WP-Mail-SMTP, where the emails are sent via SMTP in WordPress. But since last update it does not work anymore. Emails are not sent.

URL to the plugin: https://www.callum-macdonald.com/code/wp-mail-smtp/

I tested without WP-Mail-SMTP, then emails are sent.
Also if I use another contact form plugin together with WP-Mail-SMTP – emails are sent.

IP is not on spam lists.
Emails from Woocommerce are sent fine with WP-Mail-SMTP.

Can anyone help?

Regards
Kobby