Xbox One Offline Achievements

There is only a
limited queue for achievements when your Xbox One console is used to unlock achievements offline. Piling up thousands of gamerscore points offline is not likely to sync successfully.

Since achievements are ultimately logged online, you must connect your console to the internet every once in a while to sync it with your Xbox account.

Achievements work differently on the xbox 360 than they do on the xbox one.

Apart from multiplayer achievements you can earn any achievements offline on the 360,they just wont have a time/date stamp.On the xbox one you can only earn a limited amount offline before you need to connect to live & "sync" those achievements to the cloud.

Let me add this to what already said: keep in mind what is stated on the offline mode support page:

https://support.xbox.com/en-US/xbox-one/networking/using-xbox-one-offline

"When your Xbox is offline you can:

- Earn achievements (however, there's limited offline space for game captures and achievements, so you should go online every so often to sync them)"

I honestly don't know how high is that limit, but considering you said you have been offline for quite some time, maybe it applies to you. Achievements in offline mode are buggy anyway as already said.

Is there any chance you have been playing offline on the Xbox One? Achievements don't unlock while offline, but any earned offline would unlock when you connect to the Internet.

As many have already stated, the result in ban or achievement reset comes from earning achievements "offline" that very clearly require you to the "online"

For example, if you played Cod WAW on xbox 360, and you earned all the offline story mode achievements, there would be no problem. Since your account never connected online, you could never earn the dlc achievements. You also could not earn the achievements,
while being worth 0 points, for getting Prestiege 1 or 10 in online.

Enforcement will reset or ban the account that has achievements unlocked in that manor, that it specifically requires an xbox live connection.

Due to the Xbox one requiring achievements to be unlocked online, if you unlock offline, it will show as offline, but never pop offline. they will only pop once you sign back in. Even though I am not an achievement hunter anymore, if the internet goes out,
i purposely wont play a game where i can unlock achievements, as I too am paranoid about that. Thankfully, due to the nature of this, Enforcement doesnt ban or reset for achievement integrity on xbox one... they will largely act suspicious with xbox 360 achievements,
as while they are unsupported and outdated.. there are still tools floating around to modify achievements.

All in all, you should be safe, not to worry... especially if all your games are xbox one, and you dont have achievements that require online play.