Discussion checkbox missing in screen options & custom post type comment box

I’ve been trying to enable comments on my show pages but I cannot seem to get the comment form to appear. I’ve tried a number of comment plugins but each time, I cannot enable the comment box, only view the old comments. The theme i’m using doesn’t support comments on the show pages so I’ve added “comments” to custom post support. That allowed me to see comments when I added this:

<?php if ( comments_open() || '0' != get_comments_number() ){  ?>
                        <hr class="qt-spacer-m">
                        <?php  comments_template(); ?>
                    <?php } ?>

How do I get the discussion checkbox to show up so I can enable the comment box…. The theme creators won’t help.

The page I need help with: [log in to see the link]