Thank you for writing in and sorry to hear your issue, we've just updated this article https://theme.co/apex/forum/t/template-manager/20364 to adhere the new Template Manager which came in the latest version (X 6.0.1 / Cornerstone 3.0.1), that is why you seem to have a different template manager on your end. Please update your X and Cornerstone to that latest version.
Updating Your Themes and Plugins
Remember to clear all caches (plugin, server-side, CDN, and browser's cache) after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
I did check your site and yes there is no header in it even though you're using a page template that has a header. This seems to be a wrong-doing of a plugins or a custom modification on your child theme.
Please do a testing for a plugin conflict. You can do this by deactivating all third-party plugins, and see if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
If that did not work, please switch to parent X theme and see if that resolves the issue.
Let us know how it goes,