I didn't realize that I forgot to redeem the 1600 points you get from GTA V pre-order until I happened to check my xbox live email earlier today. However, the problem is that the link they provide in my email doesn't work and when I try to find 1600 points/20 dollar card on the store site, I can't seem to find it. I google it and try to click the link but it just brings me to the main microsoft store page. If anybody could provide any insight into why this might be happening, I would be much obliged.
It's been awhile since I redeemed mine but I had the same problem.
I think I got it to work by going to the microsoft store searched for a 1600 points card, added it to my cart, went to checkout, and while going through the checkout process found a place to enter a code.
I think the offer was only for a certain timeframe and now the store only sells 50 or 25 cards. Think you may be boned.