Check category_name or taxonomy slug for a Custom Post Type?

If you’re actually using categories (and not a custom taxonomy) then your $categoryname variable needs to be the slug, not the actual name. Admittedly this Wp_Query argument name is confusing.

If, however, you are using a custom taxononomy (and you’ll know if you are) then you should use 

'name-of-your-custom-tax' => 'slug'

instead.

The codex is your friend:
http://codex.wordpress.org/Class_Reference/WP_Query#Category_Parameters
http://codex.wordpress.org/Class_Reference/WP_Query#Taxonomy_Parameters

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