PBIRS - Row Level Security - Not able to assign user on the server

Hi all,

I´ve got the following problem:

I use the row level security in PBIRS and everything works fine.

But I am not able to assign user to the new Dynamic User-Role which was created in PBI Deskotp.

I have Publisher-Role and as you can see here, this should be enough to see the area "Sicherheit auf Zeilenebene" (Row level security) on the server, where you can assign user to the new role:

https://docs.microsoft.com/de-de/power-bi/report-server/row-level-security-report-server

A colleague with Administrator-Role can see this area and assign user but I´m not able to do that.

Do you have any idea, what´s the problem? 

Thank you!

Kind regards

NiHi