In Power Teacher 2.3, There are two ways to identify missing work for the Missing Assignments report.
Method One : blank grades for an assignment indicate missing assignment.
Method Two (preferred) : Right Clicking on a grade and selecting the Missing indicator.
The second method puts a red circle with an M in it, in the grade book and in the parent/student screen.
The first method is OK unless you put a zero in the book for missing work, once a zero is in the book it is not considered missing.
The second method tags the assignment as missing and allows a zero grade to be entered.
When running the report you have to select the correct method for finding missing work