not working

Hi
Please advice. I have the plugin installed and activated.
I setup a simpel test post. Here are code below.

Hej dette er en <!--more-->

Test. Læs resten testen nu<!--more--> bla clhhkhhkjhh hjjhgj jjhjjjjjh

It is not working. Just displaying post with the text..

https://wordpress.org/plugins/advanced-excerpt/