Custom post type in theme not appearing

Question

I have a theme on WordPress 4.4 which has this file included in functions.php:

<?php
function post_types(){
  $labels = array(
        'name'               => __( 'Newsletters'),
        'singular_name'      => __( 'Newsletter'),
        'menu_name'          => __( 'Newsletters'),
        'name_admin_bar'     => __( 'Newsletter'),
        'add_new'            => __( 'Add New'),
        'add_new_item'       => __( 'Add New Newsletter'),
        'new_item'           => __( 'New Newsletter'),
        'edit_item'          => __( 'Edit Newsletter'),
        'view_item'          => __( 'View Newsletter'),
        'all_items'          => __( 'All Newsletters'),
        'search_items'       => __( 'Search Newsletters'),
        'parent_item_colon'  => __( 'Parent Newsletters'),
        'not_found'          => __( 'No Newsletters found.'),
        'not_found_in_trash' => __( 'No Newsletters found in Trash.')
    );

  $args = array(
        'labels'             => $labels,
        'public'             => true,
        'show_in_menu'       => true,
        'publicly_queryable' => true,
        'show_ui'            => true,
        'query_var'          => true,
        'rewrite'            => array( 'slug' => 'newsletter' ),
        'capability_type'    => array('newsletter','newsletters'),
        'has_archive'        => true,
        'hierarchical'       => true,
        'menu_position'      => 5,
        'supports'           => array( 'title','thumbnail','comments','editor','excerpt' )
    );

    register_post_type( 'newsletter', $args );
}
add_action('init', 'post_types');
?>

Newsletters does not appear anywhere on my admin menu and I'm not sure what I am doing wrong.

Answer 1

The problem is most likely this part:

'capability_type'     => array('newsletter','newsletters'),

Try to remove it or adjust it accordingly.

You should also prefix your functions to avoid possible name collisions. So replace:

function post_type() {

to e.g.

function arcath_post_type() {

and similarly:

add_action('init', 'arcath_post_types');