The Advisor needs to have access to Assignments which is controlled via Group Page Access. To grant this access this navigate to:
  1. onCampus > Settings > Group Page Access 
  2. On the Classes Tab, select the School Year and School Level
  3. Click + Add Access
  4. Click More Roles
  5. Mark the checkbox next to Advisor
  6. Click Add Access
  7. Log out and then Log back in 
  8. Navigate to the Advisory Group > Advisees 
Note: The missing Assignment icon will only display providing there are assignments that are marked as missing, and Group Page Access is setup with access as of today's Date as per above steps. If Group Page Access is set for a future date, the icon will not display until that Date or thereafter.