http://support.xbox.com/en-US/games/troubleshooting/troubleshoot-achievements-challenges
Microsoft says you have to power cycle your X1 and wait for your achievements to sync.
If that doesn´t work, please visit the linked Microsoft Support Forums.
Good luck 🙂
Hello @CrossigSpy770
I had same problem on PS4, my solution was play last mission campaign (or the mission that you want) in online status (don't need complete it) and all achievements synchronize
Maybe you need to unlock one more achievement online to trigger all of them to sync.
I don´t know if reinstalling the game would help, but you can give it a try.
No, sorry ☹️
I personally believe that this is a Microsoft issue,
Similar things happen with certain trophies on PS4.
I could think of 1-2 more things to try on PS4, but i don´t know if the XBOX offers the same possibilities.
Maybe someone else can help you better now, I hope this will be solved.
Right, removing everything and doing all again could really work.
Sorry again, I wish I could have helped you better, but I´m running out of ideas.
But good luck, hope you´ll get everything in your second try 🤞
