Death Watch - S3-E19
Continuity mistake: At Harm's apartment, when talking to Mac about Cmdr. Krennick's advances towards him, he tells Mac that he wouldn't get involved with a superior officer, anymore than she would. However, it had already been established earlier this season in "For The Good of the Service" that Mac had a romantic relation with her Commanding Officer, Lt. Colonel Farrow.
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.