If your customer sees no content / the navigation menu in the course, then you have either
- not published a menu or the underlying pages. In this case, the customer does not see the table of contents of the products and you will not see a preview button for your product. -> Publishing course menu and pages
- the first menu is empty because it has no subordinate pages (check whether the underlying pages are really IN the menu -> Creating menu items and pages in the online course)
- the course overview is activated in the course theme, but the display in the course overview is not activated in the Contents tab in the menu (-> Designing the course overview page).
To quickly see which page and menus are unpublished and how to change that, see the article "Publishing course menu and pages."
Product page for customers without a table of contents
No preview button for the product in the backend
There is no preview button here because there is no menu / no page published.
This is where the preview button appears as soon as a page and menu is published.
Please correct this accordingly in your course.