Access to Interview Center (microsite)

Is it anticipated that anyone receiving the link (via calendar invite) should have access to the Interview Center regardless of their user type? We are seeing inconsistent ability to access the Interview Center across both hiring manager and employee user types. Do users need to be already logged into EF when clicking the link? Or is there a way to imbed a SSO redirect link? Some users are just getting a page that says “access denied” when they do indeed have the proper access.