Tell us what you are trying to do? I am using a child theme of twentyseventeen default theme.
I have several template files for using with posts and or pages. When creating a new post I just choose the template from the Template drop-down in the editor which gives me the layout I want for each particular post.
When I creat a custom post type the drop-down to choose the template is not available.
Is there a way to show this in the editor?
Is there any documentation that you are following?
Is there a similar example that we can see?
What is the link to your site? The posts ae not public as yet.
my child theme supports custom post types.
It displays the post attributes template choice for the products post type from woocommerce.
I wrote a books custom post type to test further, it also displays the choice of template.
The only custom post types not showing are those written by Toolset, even though I have added support for them in the template file. see attached image.