Achievements not unlocking on Xbox One S

To fill in some "blanks". Actually, every Achievement Unlocked has a few methods of the order it appears. If you Unlock an Achievement and view it from your own Profile it will simply show in the order the Achievements were Unlocked.

If you Compare Games with someone else (Friend or not doesn't matter), it will show both the combination of your Achievements and their Achievements but in the order they Unlocked the Achievement/s.

If the other Player has Achievements Unlocked that you do not, it will show in the order they Unlocked the Achievement/s with yours showing Locked directly across. If you have Achievement/s Unlocked that they do not it will be at the bottom of the Compare Games
in order of which the Achievement/s were Unlocked from your Profile.

Are Xbox One achievement s working properly? Have you possibly already unlocked those achievements on the 360?

Are you sure you’re meeting all of the requirements?

Achievements unlocked while playing on a series S/X aren't separate,they're just the same as xbox one achievements.

It's not like the xbox 360 & xbox one where the achievement system was made slightly different,the xbox one & series consoles use the same achievement system.

Hello I have completed the fly squatter achievement for xbox one s for assasins creed 2 but it never unlocked

It was defo an achievement for 100g complete the game on hard. When I add all achievement unlocked on xbox one it 5370 when I look on 360 at compare game s its says xbox one 5270