Trouble with an Achievment

I completed the fifth mission in Halo 3 on the Heroic difficulty; but it didn’t give me the achievement for it.

What should I do? Is it something I can fix?

Hi DoctorTaco123,

This sounds like an issue with Xbox Live and thus is out of our scope. We recommend you reach out to Xbox Support in one of the following ways:

[/li]- Xbox Support on Twitter