You have been just granted the authorization to add new users in SYSVIEW, but on the "SECURITY, Security User IDs" panel you cannot see the "newuser" entry, which is required to add new users, on the list of the users.
SYSVIEW 16.0 & SYSVIEW 17.0 - z/OS supported releases -
You need to exit from SYSVIEW and then to enter again to have the "newuser" entry displayed on that panel.