Thats what I wanted to know....any answers out there
If you are talking specifically about the mission where you have to defeat duke as part of a team and that mission has timed out. You will need to acquire more agent standing in order for it to pop up again.
NPCs are attacked 2-3 times a day so keep an eye out for when those fights go down. (Currently) They normally happen at 13:00 , 18:30 and 00:00 Torn time. With exceptions sometimes are changed an hour or half an hour after this set time.