I spent some hours to find the reason of this problem.
I have inactivated our plugin and deleted wri_template folder from the Layers theme folder, but the header-page-title.php partial template of Layers theme does not displayed on post pages.
I have tried to debug the problem, but I cannot find any problem in our plugin that causes this problem.
At the end, I have created a brand new WordPress 4.7.1 environment, and install Layers 1.6.5. without WP Related Items and WooCommerce and any other plugins.
I tried to find any customization possibilities in Layers for switching on/off this header title and breadcrumbs section, but I cannot find any settings, thus I leaved the default settings of the theme.
I have created some posts, but the header page title with the breadcrumbs did not appear in the post pages in my new WP environment.
Please help me what I have to do to appear this section in my new WP environment. Then if Layers displays this section in this simple environment, we can install WP Related Items and see if the plugin has any effect on this Layers section.