WP Query doesn't show custom posts in custom template

So I’ve read that WP_query is a better option to use than query_posts in using to query a list of posts.

But I’m unable to get it to work with the code below

<?php $args = array('post-type' => 'sermons', 'meta_query' => array(array('key' => '_wp_page_template', 'value' => 'my_template.php'))); ?>
<?php $sermonposts = new WP_Query( $args ); ?>
	<?php while ( $sermonposts->have_posts() ) : $sermonposts->the_post(); ?>
		  <h2><a href="<?php the_permalink() ?>"><?php the_title(); ?></a></h2>
    		<p><?php echo get_the_excerpt(); ?></p>
<?php endwhile; ?>

But the 2nd block of code does work:

<?php query_posts(array( 'post_type' => 'sermons') ); ?>
<?php while (have_posts()) : the_post(); ?>
    <h2><a href="<?php the_permalink() ?>"><?php the_title(); ?></a></h2>
    <p><?php echo get_the_excerpt(); ?></p>
<?php endwhile;?>

These blocks of code reside in a custom template thats not currently being selected in the CMS on the right hand side drop down(when it is the WP_query still doesnt work) and this is pulled in from the default page.php with conditional if(is_page) underneath the default code with the following line

<?php get_template_part('page-posts-display-template', get_post_format() );?>

Any ideas why the recommended option isn’t working in this case?
Thanks in advance.