i have heard there has been a few issues with the achievements not unlocking in Ghosts.
i have recently completed mayday completionist and didn't the achievement unlock.
i tried again in case i missed something and still the same issue, i tried a public match, and completed it, the 3 other friends unlocked it but it didn't pop for me again. so i talked to support and they were no help at all...
i tried hard reset. removing my profile and then putting it back on xbox one. still no joy.
i have tried turning the instant on, off like it mentioned on another forum, but again no luck.
maybe its delayed like some people say but this is really bugging me.
and it wasn't done offline so if anyone has had similar happen please let me know
A support case was created for you and you should be contacted shortly by a Customer Support Representative, if you haven't been already. You can view and update your case at the Activision Support website. After logging in, go to "My Support" then "My Cases".