sirs, I'm using Membership plugin for creating a premium

Hi sirs,
I'm using Membership plugin for creating a premium contents web site.
I'm using categories to classify contents:
one categorization has an editorial function ("Primo piano", "Riviste" and "Rassegne" and its subcategories) and the others categorization is used to divide free contents from premium contents ("Abbonamenti" and its subcategories).

The site is http://www.entilocali-online.it

If I navigate the site with not logged user = free level (I set that "not logged users" = "free level") something strange appened:

1) Home page: if I click on contents I can see the free contents and I receive a message of subscription if I try to access the premium content. That's OK ( http://www.entilocali-online.it )

2) If I click on the archive of month, I see the list of contents (free and premium): if I click on contents I can see the free contents and I receive a message of subscription if I try to access the premium content. That's OK (www.entilocali-online.it/2014/07/ )

3) If I try to nagivate a category ("Primo piano" or "Rassegne" or subcategories from the main menù" ) that contains free and premium contents, I cant' access to the list, to the free or to the premium contens. Nothing. ( http://www.entilocali-online.it/category/primo-piano/ ).
I suppose it is NOT CORRECT.
I think that the right way should be to have the list of contents of a category (similar to monthly archive) with title and incipit of all articles of the category.

Federico