I am a little confused. I need to hook into the Events plugin so when a user RSVP’s it runs a function to add the user to our client’s MailChimp account.

The plugin’s Docs give this

do_action( 'event_tickets_rsvp_attendee_created', int $attendee_id, int $post_id, string $order_id, int $product_id )

which can be found here: https://docs.theeventscalendar.com/reference/hooks/event_tickets_rsvp_attendee_created/

I have written something simple to test:

function my_custom_function() {
?>
<script type="text/javascript">
    console.log('TEST')
</script>
<?php
}
add_action( 'event_tickets_rsvp_attendee_created', 'my_custom_function', 999 );

Unfortunately I can not get any results. Can someone point out what I am doing wrong or better yet what I need to do to achieve my goal?

Thank you