I suppose this is the correct thread to post this. If there is a different thread that is for achievements not working, I can go there.
Yesterday, I completed mission 5 (Arcadia Outskirts) and I did not receive any achievements. I also collected the skull and black box, and I did not receive progress on those achievements based on my Xbox achievements section. (It still says I only have 4 of each -- I have gathered all from the first 5 missions, counting this last one.)
I actually completed mission 5 twice due to my missing a Wraith for the skull the first time. The achievement for completion did not pop either time.
I also am confident I hijacked at least 6 vehicles with Spartans during that mission for the "He's Got the Jack" achievement. This achievement did not pop either.
I checked this morning, and none of the achievements have popped still. No further progress of skulls/black boxes achievements have shown yet either.
If anyone has any information on this, it would be appreciated. Thank you.
EDIT: So, I hard reset my Xbox and my achievement are working again. I did need to replay the mission to get them though.