Dynamic RLS

Hello! I am trying to set up dynamic RLS for some of my reports. I can't seem to get it to work. I have followed several videos, and they all seem to say that you need to cross-filter "both" and apply the security filter; however, when I set up the role [email] = USERPRINCIPALNAME(), it gives this error message and won't let me go further. I have the userprincipalname() function and set up a dimension table with their username, emp. ID and email. When I proceed without the security filter, the role doesn't work.