Empty posts with category

I’m trying to get all post from a category and type using this:

?json=get_category_posts&category_id=58&post_type=type1

And I get this response:

{“status”:”ok”,”count”:0,”pages”:0,”category”:{“id”:58,”slug”:”type1″,”title”:”Type1″,”description”:””,”parent”:0,”post_count”:1},”posts”:[]}

So, if there is one post, why it isn’t listed?

Also if instead of category_id or id I use slug=slug_name, the response is a 404.

Thanks.