Achievements not unlocking and slow performing Xbox

So, since March you were not able to unlock anything.

I know that the achievements of the game are so slow. I was playing yesterday and it was so slow the process.

The quest unlocking might be slow because of the xbox hall of fame contest going on. Thousands of gamers worldwide unlocking achievements at the same time could cause some issues. I remember awhile back when they had a rewards quest to see how many achievements
you could get in so many days, achievements wouldn't unlock for three days. You could try loading the game for the next two or three days and even trying to unlock an achievement for another game to see if that helps. Or even resetting your xbox as well.

Halo MCC is known for having slow to unlock achievements or slightly buggy achievements. My advice would be to try hard resetting your box first, and then loading into one of the missions, beating it again or just quitting out and seeing if it unlocks
then.

Hi,

To successfully unlock achievements and challenges, you need to make sure the following are true:

• You have completed all of the required elements to unlock the achievement. You may have to unlock a combination of achievements.
• Your console must be connected to Xbox Live. To complete challenges and unlock achievements, your Xbox One console cannot be set to offline.

If you are experiencing issues with your game achievements, you can perform the suggested solutions on this

link.

Let us know how it goes.

As for now, the achievement unlocking system has changed a bit. Everything is performed server-side. So if you "unlock" achievements whereas you are offline, they will be unlocked the next time you connect to Internet.

I suggest you post your request on
http://xbox.uservoice.com to see that feature come to Xbox One in the future.