Why is it that I don't receive Achievements in Halo Wars For Xbox 360?

[Max]

I started Playing Halo Wars A few days ago but I played offline. (internet cable pulled out)

After receiving one achievement (I think it was 50G for finishing the 2nd chapter) I retrieved my Gamertag on someone Else's hard drive.

I knew I would lose that achievement but I thought I could just replay the level and get it back

After That I removed my hard drive and placed it on a different Xbox 360 after putting it back on my own Xbox and retrieving my gamertag again I saw that I lost Halo Wars save files. That wasn't that big a problem.

I just noticed that I couldn't receive achievements after replaying some levels all over again.

I am all the way through the 11th level and i'm pretty sure I should have received some achievements by now for clearing some levels.

I did receive a Achievement but it was for clearing an objective not for finishing a level.

So the question is why am I not receiving the achievements?

Hope I gave enough detailed.
Thanks to anyone answering.

 

[Mysterious Answerer]

Ummm my guess is that when you get an achievement when your offline and retrieve your gametag on someone else's hardrive you will lose this i think when you lose that achievement you won't gain it again because you have all ready obtained it plus i think you lose achievements and save files when you switch your hard drive into a different xbox.
I don't really know why it does this but ask microsoft or Xbox live whats going on they can probably give you a full detailed answer then this one i'm giving to you.

My guess is not to do this with any other games and try and get more achievements online that way you won't lose any.