Not Found

Hi. I’ve followed the video on how to setup and create the first page and lower level document. The page shows ok when the shortcode is added.
But when I select from the menu I get:

Not Found

The requested URL /wp/docs/this-is-my-first-doc-it was not found on this server.

I’m confused as I have followed the instructions. What am I doing wrong?

Kind Regards

https://wordpress.org/plugins/slick-doc-it/