Unable to install dutch language

Hi there,

I’ve searched this forum, but did not find an answer.
I failed to change the english language to dutch in the contact form.
To install the dutch translation for Contact form 7, I did this:

* set the general WordPress language to dutch and also in my user profile after downloading and installing the dutch language pack
* download .mo and .po files from here
* copied those files into wp-content/plugins/contact-form-7/languages/ and changed the names to wp-contact-form-7-nl_NL.mo and wp-contact-form-7-nl_NL.po
* make a new contact form and paste the code into a page content

Everything is still in English.

I did the same with another plugin (opening hours) and that works.

Help would be useful. ??