INFORMATION ON ACHIEVEMENTS AND LASO PLAYLISTS

I completed halo 3 Laso playlist with three of my buds and only two outta four unlocked the achievement . It says my buddy and I need to complete the epilouge yet we clearly can’t do that since it starts us from seiraa 117 . But all progress is there.

You might post here about this:
https://www.halowaypoint.com/en-us/forums/84ad72a8b51847978545f685f651fc15/topics/achievement-progress-unlock-reports/d3a61929-3917-4224-b723-be59860816e8/posts?page=38#post752

May not see any additional help. Something to contact MS game support about if nothing happens.

Yoo that link isn’t letting me click it it’s just part of the message