The title doesn't actually make it clear what you're reporting.
Can you please confirm exactly what code you're putting where and what the results are versus what you expect? Clear reproducible steps are usually preferred.
Widgets with no position will not appear anywhere, but you can call the configured widget instance directly in templates using the <xf:widget key="widget_key" /> syntax.
This would usually only be visible if you have the categoryOwnPage option enabled and you go to a dedicated page to view a specific category. By default this isn't enabled as we just use anchors to point to specific categories on the forum list.
What is the last party of the URL of the page you're expecting to see the widget you've added to the category_view page? Is it like categories/category-name.1 or is it #category-name.1 or something else?
What is the last party of the URL of the page you're expecting to see the widget you've added to the category_view page? Is it like categories/category-name.1 or is it #category-name.1 or something else?
It's the landing page, the equivalent of https://xenforo.com/community/. Moreover, the test board is a clone of the production one which does display the widget.