Note: You are currently viewing documentation for Moodle 3.1. Up-to-date documentation for the latest stable version of Moodle is probably available here: error/moodle/cannotviewprofile.
You do not have permission to view the profile page for this user.
You are most likely seeing that because you are attempting to view a user's profile from outside of a course. As an Authenticated user you are, by default, not permitted to view other users' profiles. You can ask your site administrator to change this setting if you do not think this is correct.
You are also (normally) permitted to view the profiles of other user's on the same course, typically via the People block on the course page.