Achievements not unlocking when I achieve said challenge?

I've encountered this problem myself, and it just fixed itself. It took a while, but the achievments just randomly popped, in fact they actually popped while playing another game... was strange lol

There is a small support article here:
support.xbox.com/.../troubleshoot-achievements-challenges

When I checked my achievements it showed it as "Unlocking" or "Processing" or something along those lines, but as I said, it did unlock eventually

What does 100% is a bug in the current update it'll be soon patched hopefully. The done unlocking is what you'll see when done unlocking a achievement. I hope i cleared stuff up

Achievement support and help: https://support.xbox.com/achievements-and-challenges

Hello KnockdownTree,

Thank you for posting here on the Xbox forums. Were you connected to a network when you completed the requirements for this achievement?

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.
  
  Note 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 haven't already, check out this support link : Problems with Xbox One achievements and challenges

Hi Elliottrumbold! My name is Ricardo an independent advisor ready to help you with this situation!

To successfully unlock achievements and challenges, make sure that the following are true:

You’ve completed all the required elements to unlock the achievement.

Note Make sure that you read the description for the achievement or challenge carefully. You may have to unlock a combination of achievements or challenges to unlock your rewards.

Completed achievements that are pending confirmation from the Xbox network are listed as "Done! Unlocking." This means the achievement will be processed in the order that it was sent to the Xbox service, and it might take some time to be confirmed.

If you meet the requirements to complete the achievement or challenge, but you don't see the “toast” icon or the achievement isn't listed, try the solutions below.

Your console must be connected to the Xbox network. To complete challenges and unlock achievements, your Xbox console can’t be set to offline.

https://support.xbox.com/en-US/help/games-apps/...

Achievements don’t unlock instantly when you complete them

In some instances, you may meet the requirements to unlock an achievement but not immediately receive a notice or update to your gamerscore. The Xbox Live service validates the unlocking of achievements and, though rare, delays can occur. Don’t worry – your
progress has been recorded and the achievement will be awarded shortly, usually in less than 24 hours.

Achievements and challenges not unlocking while offline

For achievements and challenges to get unlocked and for rewards to be issued, you must have an active connection to Xbox Live. Though you may be able to meet the requirements for an achievement or challenge while offline, you will not receive related notices
or rewards until you connect to Xbox Live.

A challenge disappeared before you could finish it

Challenges are time-limited, sometimes to weeks or months, sometimes to just hours. If you don’t complete a challenge within the time window it’s available, you will not receive a reward.

No gamerscore earned from app achievements

You can earn app achievements for basic use of an app (such as, watching a movie on Netflix), at the app developer’s discretion. App achievements do not affect gamerscore, though they may bring other in-app rewards.