Complete the following to resolve the issue: 

Check the Report Card to ensure that attendance has been marked to be used and that the correct groups are being used.

1. Navigate to Academics > Grades > Report card setup > Report card builder (old).
2. Filter for the appropriate Year, Level and Style, then click the View button. 
3. Click Edit next to the report card.
4. Check to make sure at least one group is checked off.
5. Also check to determine if any Attendance types (Absent, Tardy, etc) are checked off.

Attendance on Report Cards is driven by the Attendance Record Method.
As an Attendance Manager:

1. Navigate to Academics > Attendance > Attendance Setup
2. Click the Record Method tab

The applicable absences are indicated by a red "swoosh" on the Attendance tab of the Student's Academic Profile. If there is no red "swoosh" icon for a student's attendance, this indicates that the absences were either not recorded during the meeting time as set on the Record Method screen, or the Schedule Set selected on the Record Method screen is NOT the schedule set the class is tied to (where the absence was recorded).