Same Problem here.
ENTER CODE HERE:
The code you entered is not valid. Please try again. Please note that the code was printed in upper case to help identify Ls from 1s.
The in-game content will be applied to all linked console accounts.
DO NOT REDEEM FROM A MOBILE DEVICE OR CONSOLE.
I tried it so many times...
I live in Germany and I used the link from your post to try redeeming my Bonus Content
https://profile.callofduty.com/ghostsce/redeemCode
Please help me.