Print message if no tickets are available

no-more-ticket-sales.php

<?php
/* If there are no tickets available for a future event, or the event is in the past,
 * Then a message will be shown to the users on the single event page.
 *
 * For The Events Calendar and Event Tickets plugins by Modern Tribe
 * Author: Andras Guseo
 * Last updated: May 1, 2017
*/

add_action( 'tribe_events_single_event_after_the_meta', 'no_tix_message' );

function no_tix_message() {

  if ( tribe_events_count_available_tickets() <= 0 || tribe_is_past_event() ) {
    echo "Sorry, there are no more tickets for this event.";
  }

}