The issue with the above link is that they are trying to access the static url part only of the dynamic page url. They needed to add the dynamic part of the url after that static url part.
Have a look at this tutorial for a simple members profile page which creates two dynamic members profile pages for each member.
https://support.wix.com/en/article/corvid-tutorial-building-your-own-members-area
You will notice on the first dynamic page they have done the link above in their code, however it is followed up by a dynamic bit in the {ID), in this tutorial it is highlighted as a ID block.
https://support.wix.com/en/article/corvid-tutorial-building-your-own-members-area#profile-page
So like this Yoursitehere.com
The same with the second dynamic page for the update profile page where they add the /Update/{ID}.
https://support.wix.com/en/article/corvid-tutorial-building-your-own-members-area#profile-page