The SLUG in CoursePress Pro won't update

The SLUG in CoursePress Pro won't update;
https://norskdemo.growdly.org/wp-admin/admin.php?page=coursepress-pro_settings

I will like to get the virtuelle SLUG to work. I have tried to update the /wp-admin/admin.php?page=coursepress-pro settings so all the slug is new, but it is not working. Many times we are getting:
Oops! This page does not exist.
It appears that nothing was found at that location. You can try one of the links below or a search?