Are you trying to get Northstar and Juggernaut's challenge missions from Mission 6: Priorities?
if so I know you have to be a brotherhood to get Juggernaut's mission to work.
As for Northstar you'll have to be a X-Men for sure.
Are you sure you stuck with the right choices along the way?
Mix matching your choices can cause problems and challenge missions won't be give. if your Faction isn't right.