Can't get locales to work properly

Question

So I've setup locales following the official guide and am going with the option where English (en_gb) is the default and Danish (da_dk) is in a sub-folder:

http://mysite.com --> en default
http://mysite.com/dk/ --> dk sub-folder

In summary, I've set the locales in Settings -> Locales

I've enabled them for my section (which is a channel):

I've set the siteURL array (single domain config):

'siteUrl' => array(
    'en' => 'http://mysite.com',
    'dk' => 'http://mysite.com/dk/',
),

I've created the folder structure and copied the index.php file and .htaccess file across to the dk/ folder:

craft/
public_html/            --> mysite.com/
    .htaccess
    index.php
    dk/                 --> mysite.com/dk/
        .htaccess
        index.php

And I've made the edit to the dk/index.php file:

// Path to your craft/ folder
$craftPath = '../../craft';

// Tell Craft to serve the Danish content
define('CRAFT_LOCALE', 'dk');

Viewing my entry in English works fine:

http://mysite.com/segment/title  --> Shows in English

Viewing the same entry in Danish directs to:

http://mysite.com/danishsegment/title --> Missing /dk/ in URL. Nothing shown

So the preview link for Denmark doesn't include the country segment in the URL (dk/) and results in a 404. Even manually adding dk/ to the URL results in a 404. It doesn't seem to be recognising the Danish locale at all.

Any ideas as to what I'm doing wrong?

UPDATE:

Here are the contents of my .htaccess files. All standard Craft with a Type to ensure PHP 5.6 is used:

AddType x-httpd-php56 .php

<IfModule mod_rewrite.c>
    RewriteEngine On

    # Send would-be 404 requests to Craft
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_URI} !^/(favicon\.ico|apple-touch-icon.*\.png)$ [NC]
    RewriteRule (.+) index.php?p=$1 [QSA,L]
</IfModule>

UPDATE 2:

The 'Offers' section (Channel) is set to have a different URL for each Locale:

Answer 1

Have you tried putting da_dk in as the key in the siteUrl array?