Completed the campaign, no achievement

I’ve completed the entire Halo 4 campaign on Heroic and haven’t received any of the campaign completion achievements (i.e “Wake Up, John” or “I Need A Hero”). My service record indicates I’ve completed it all but when I go to the mission listing 2 missions aren’t completed (Forerunners and Infinity).

Has anyone else experienced this? If so, how’d you fix it?

I have almost the same problem. I didnt get the achievement for the mission ‘Infinity’ and when i go to campaign it doesn’t say i’ve completed it, yet the missions after that are unlocked. Then, I went back and re-played the mission and still didn’t get the achievement. I’m mad at Halo >:(