wp_link_pages page2 innacessible

Hello,

I have a difficulty figuring out how to use wp_link_pages() function.
I’m using this function in my single.php file ( within the theme ) and at the end of the post i’m able to see: Pages 1 2 (if I use <!–nextpage–> tag within that particular post).
I have permalinks activated like this :
/%category%/%postname%.html, so my post url looks something like this :
https://ubuntu/wordpress/category-name/post-name.html
and when I click on 2 it redirects me to something like :
https://ubuntu/wordpress/category-name/post-name.hml/2
The latter URL doesn’t do anything, and I get redirected to the first one.
Can anyone give me a hint on how should I use/modify wordpress for this ?

Thanks in advance.