Please ensure that you meet the requirements for the given achievement. You may check that with resources that can be found online. If you met the requirements and the achievement didn't pop up, make sure that your internet connection is established and stable, and try to clear the cache of your Xbox as instructed below. This will not erase any of your games, data or saves.
1. Power down your Xbox using the Xbox controller or the Power Off button on your Xbox
2. Unplug the power cable from the back of your Xbox
3. Wait at least two minutes
4. Plug the cable back into your Xbox
5. Turn your Xbox back on
Afterwards, if the achievement was not granted automatically after launching the game, please try to trigger the achievement once again (you may need to load a gamesave before meeting the requirements).