Well, according to your profile, you are labeled as a cheater, for the whole community to see. You evidently modded your gamer score, and you are responsible for your own account. The achievements you previously earned are not achievable on that account
anymore hence you modded the gamer score to illegitimately earn the achievement(s).
Did this solve your problem?
Sorry this didn't help.
Great! Thanks for marking this as the answer.
How satisfied are you with this reply?
Thanks for your feedback, it helps us improve the site.
The only people who can tell you exactly why you were issued a gamer score reset are located
But the most common reason is because you modified your gamer score via third party software on your PC. Once a gamer score reset is issued it is permanent. You will never be able to earn any achievements, on either account that
was reset, on any games played prior to the reset. If you wish to do so then you will need to start fresh with a new account, this time hopefully earning them legitimately. If not then the next course of action would be a permanent account ban from XBL. That
would mean you would lose everything associated with that account including; ms points, Live time, gamer score, game saves and download content.