Users will only be able to access Stratum.Viewer if they have a user profile that has been assigned to a user profile group. Additionally, the user must have a role attached to their individual user profile or to their user profile group.
Other facts about the related nature of user profiles, groups, and roles:
If a role is attached to a user's user profile, the user will have a role that is unique from other users assigned to their user profile group.
If a role is attached to a user's user profile group, the user will have the same role as all other users assigned to that group.
A role definition will not be active in Stratum.Viewer until it has been attached to a user profile or user profile group.
Users who have a security administrator level of access, as defined by their user profile, do not need to be assigned a role. Security administrators have access to all dimension members and measures in all Analysis Services databases registered with Stratum.Viewer.