Code for GOW1 not activable

False, the Gnasher did NOT dominate in Gow1&2. It's the players who dominated with it. You ever use a Gow1 Lancer? It was almost as strong as the Retro Lancer, you seen the Gow1 Longshot? Actives would down you no matter where you shot the foe at, Gow1 Hammer?
Infinite Ammo. It was not hard to kill people in Gow1&2 with weapons other than the Gnasher.

i have the same problem with codes of gow1, gow2 and gow3

I'm surprised you don't have pictures of a noob tube and the ak74u with rapid fire in your sig. Or maybe a GOW1 active reloaded sniper.... Those weren't OP either.

I found a solution in another forum.

As I live in Andorra and my account is set to Spain, it seems that there's some kind og regional protection (maybe for violent content) that makes that in some countries the code of the games is not accepted.

So, I used a free VPN for simulating that my computer is in Spain (I used "tunnelbear", it's a free VPN), then went to the web of Xbox.com (not directly in the console) for redeeming the code, and the codes of GOW1 and 3 were accepted, now the games are
dowloading to my console.

If the problem is that there's a regional protection maybe the people of Microsoft should explain that in the error screen, not that "something went wrong", the same with the online support.

I hope everybody else finds a solution too.

does your account region match you actual region if not that would be why

You must change it under my account and change my region on this website )not locale fyi) and there is a 3month waiting period to change back

Then change it on your console