Not getting H2 LASO achievement

Games Halo: The Master Chief Collection
1

Hi all,
I finished Halo 2 LASO by myself a few months ago and still havent received the achievement, even though the progress of my H2 LASO playlist is showing 15/15.
I’ve done 1,3 & 4 on LASO, and got the respective LASO achievements, so this is a unique issue for this game.
Any suggestions, fixes etc.?

EDIT: You can see a screen-cap of my playlist progress here:

Thanks.