Page Builder CSS not loading on custom post templates

Hi, I’m a big fan of the SiteOrigin page builder and use it frequently on my WordPress sites. Today I ran into a problem: the CSS isn’t loading when I use it on certain pages.

I have tried on different installations of WordPress
I have tried deleting and re-installing page builder
I have tried deactivating all plugins
I have made sure the appropriate post types are enabled in the Page Builder settings
I have tried on different themes

Page builder does work on default WP themes and earlier themes I’ve built, but not on the current theme I’m working on. I’ve done a bit of digging in the plugin documentation and it seems that there are no supporting functions required to enable the css and that the content filter is the only thing required.

The single post template displaying the page builder concept relies on a very rudimentary loop:

<?php 

get_header(); 

if ( have_posts() ):

	while ( have_posts() ): the_post();

		echo '<div class="main-content">';

			the_content();

		echo "</div>";

	endwhile; wp_reset_postdata();

endif;

get_footer();

Is there anything I’m missing here? Any help would be greatly appreciated :)