Custom Post Type Permalink Problems

Hello,

I have created a custom post type as seen below,

function transactions_register() {

$args = array(

    'label' => __('Transactions'),

    'singular_label' => __('Transaction'),

    'public' => true,

    'show_ui' => true,

    'capability_type' => 'post',

    'hierarchical' => false,

    'rewrite' => array("slug" => "transaction"),

    'supports' => array('title', 'editor', 'thumbnail')

);

register_post_type( 'transaction' , $args );

}

I have set my permalinks to be like this /%category/%postname however when I navigate to a transaction, the URL looks like this,

http://www.domian.com/transaction/test

However this returns the following server error

The page cannot be found

How can I make it so my custom post type will work with my permalink setting?