[Plugin: Breadcrumb NavXT] Not Displaying Categories in page

What do you mean by “go in a page of the subcategory”? Are you talking about a second or third page of the subcategory’s archives? Are you talking about a post that is a member of that subcategory? Or are you talking about an actual page? If you are talking about an actual page (post type), the output you are seeing is the expected output. Pages (the post type) don’t have taxonomies, they use other pages (the post type) for their hierarchy.

I’m talking about a page i have attached to a category.

>>>>>> Pages (the post type) don’t have taxonomies, they use other pages (the post type) for their hierarchy.

I use a plug-in “Category Page”, so i can attach pages to categories, like posts.

There is no possibility to have hierarchy for pages with breadcrumb ?

Pages only follow the page hierarchy as they are hierarchical elements and have a clear parent-child relationship. Taxonomies are only meant to be hierarchies for flat post types which do not have a clear parent-child relationship. Use a CPT if you want a hierarchical post type to have a taxonomy as it’s hierarchy.