Nbgrader and jupyterhub 2.3 configuration problems

Hello everyone,
I try to configure nbgrader (0.82) and jupyterhub (2.3.1). I managed to set up a service following the demo examples provided with nbgrader (nbgrader/demos/demo_multiple_classes at main · jupyter/nbgrader · GitHub).

But I still have some issues left. 1. Instructors cannot add users to courses (at least not via webinterface of the service) 2. Instructors can add an assignment but they cannot access it (via webinterface clicking add new assignment is possible, but clicking on the assignment is not)
(As a side note if I go to the assignments tab (as student1 or instructor1) i do not see courses it states no courses found, but that might be because I failed to have users in courses.)

I assume it is because I set up the notebooks with user settings allowing only assignment list (and not formgrader, create assignment or course list).
So instructors have acess to the services but I assume miss some rights.
With the demo there is a setup (setup_demo.sh) where instructors and students are given certain permissions, but I do not know how to apply this to my existing jupyterhub. I cannot simply run enable_course_list instructor1 because such a command is not found, but I do not know where I can set s.th. like jupyter labextension enable nbgrader/course-list for instructors.

Any hints, where I can set this? Or on how to create a configuration that allows adding course users and creating/managing assignments?

That the webinterface not working for me was due to an cookie problem. After a fresh start with a cookie-free browser, using the webinterface is working.

I still cannot click onto an assignment that I created using the add assignment-button. And create a set of problems within a notebook. Some rights might still be off.

When I try to use the command line in a terminal owned by an instructor i get this message when trying to add a student to a course:

Make sure you set a valid admin_user ‘api_token’ in your config file before starting the service.

This was the command:
nbgrader db student add test-student --last-name=Test --first-name=First --CourseDirectory.course_id=course101