I've got the builder installed and working and activated for a Content Type. I can edit the Content Type with the builder to override the default output of the Content section. However, I can't add any builder content. The theme doesn't allow the builder to overlay the regions onto it. I updated the module config file. I think it's a problem with the theme, because my main content area doesn't have a wrapper, even when I turn on dev tools. Have you heard of this before? It's an Omega subtheme. In theme/mytheme/templates/system/html.tpl.php all it says is  <?php print $page; ?> for the main content. Is this the problem?