Problems acquiring achievements xbox 360

Hello, I am having an achievement problem where I cannot gain achievements in a long list of games I cannot both gain achievements and it claims I have no achievements for them games when I have successfully completed the requirements for the games.

The list of games include:

Gears of war

Gears of war 2

Guitar hero 3

Halo 3

Resident Evil 5

Assassin's Creed (1)

Halo 3: ODST

(and many more)

Let's take Gears of War 2 for example

I have completed the game on Insane (Hardest Difficulty) which as it states in the achievement is the requirement and the achievement is still not unlocked under my account.

(Achievement: https://i.gyazo.com/e7ecaff3d1079bfee16a76cc13ad5ac2.png)

Since it did not unlock I have gone through the xbox support article trying to find a solution using this article Uh oh... that shouldn't have happened. and after using step 2 on xbox 360 it knows I have both at least
completed the game once and on insane as in the war journal on the game the requirement to play on insane is ticked (complete game once) and going onto campaign and selecting an act has a tag at the end of it showing the hardest difficulty I completed it on
which is the icon for insane.

Any assistance would be greatly appreciated.

~

:)

 

Strange issues with acheiments

Ok so a while ago i lost all of my Xbox 360 achievements due to a friend illegitimately acquiring achievements on my account and at the time i didn't really play 360 anymore because id moved on to the Xbox one recently i started to play 360 again to earn
back what i lost but

The achievements wont unlock and when i look a the achievement progress on the Xbox one for any 360 games it has an unlock date underneath and so i need help to fix this issue and any help would be appreciated

 

Tom Clancy's Rainbow Six Siege

It's a shame, put yourself in my situation. I have problems acquiring the game.

 

UPDATE: I have unlocked the achievements as I have 100%'d gears of war 2 however it says I have 0g and 0% complete

i.gyazo.com/f39a9baa1ccf341226fec93a1dd83fed.png and I beat the game on insane back in 2009

i.gyazo.com/a45799aaa4ddea1cf87cd3467e4732a6.png

 

Monkeycookie;

You may wish to log into your account at
http://enforcement.xbox.com to see if you have received any enforcement actions against your account at some point; specifically a Gamerscore reset. A Gamerscore reset would result in the symptoms you are describing.

 

I have a "Perfect Record"
i.gyazo.com/fd3b365402dd108b3783380afcdee79c.png