lgromanowski on "[Plugin: Polylang] zh_CN post gives 404 error"

Hi,
at first big thank you for a great plugin! :)

I'm running https://openmw.org/ site and one of our users is trying to do some translations in Chinese language (zh_CN). The post is written and all things related to language are set-up in similar fashion like we do with other languages but it gives us 404 error:
https://openmw.org/zh/

Direct link to post is working:
https://openmw.org/2012/12/17/%E6%9C%AC%E5%91%A8%E5%9B%9E%E9%A1%BE-2012-12-08-ap0/

Our polylang settings are here:
http://i.imgur.com/pBkS2.jpg?1

Would you help us with this, please?

If you need any other details please let me know.

Best regards,
Lukasz