Continuity mistake: After Harm's cockpit canopy is smashed, he and Ayers continue to fly with their masks off - one would have thought that wearing oxygen masks would have made things easier in that situation.
Continuity mistake: When Lt. Roberts is held hostage in Admiral Chegwidden's office with the Admiral and the Major, he mentions a sister named Winifred. She is never mentioned again throughout the series. In later seasons it is implied that Lt. Roberts only has one sibling, a brother named Mikey.
Answer: Officially, the individual has been ordered to attend, failing to could be interpreted as either, Failure to follow orders, dereliction of duty, going AWOL, or even desertion. It would depend on the underlying reason as to why the person doesn't appear.