If it doesn't come soon you will need to contact GameStop and let them know. There is nothing that can be done here. I purchased mine at Game Stop and I had the code in my hand when I left the store.
It is instant so you should already have it.
When you get it sorted out then check out our clan https://elite.callofduty.com/connect/clan/view/938317 Section 8. We would love to have you join us we are 13 pts from lvl 10 and dbl xp.