Multilingual site page not found error on default language URL path prefix

Question

I have a multilingual site with 3 enabled languages.
Default language is Dutch. However when going to http://MYSITE.com/nl I receive a page not found error. /fr and /en is working as usual.
How can I use /nl for my Dutch content? When using the user interface text block to display language links, on a /nl page the NL link is set to active.

Answer 1

On admin/config/regional/language/edit/nl Path prefix language code was set to empty. Setting the code to /nl solved the problem.