Troubleshooting: Singular layout appears in post preview but not actual post (Themer)

If you have a Singular theme layout type set up with a Post Content Settings module, when you edit individual Posts you must add content in the WordPress Text Editor, not Page Builder. If you format post content in Page Builder, the theme layout is blocked from being applied to the post. 

To ensure that your Singular theme layout works as planned, disable Page Builder from Posts by going to the WordPress admin panel and choosing Settings > Page Builder > Post types, then clear the Posts checkbox.