I believe that promo code is expired, unfortunately.

When did you receive the email?

I used that code almost a week ago and it worked for me. Try in game if you used it on this site or try on the site if you already tried in game. Or try all caps maybe. Some of these codes do seem hit or miss tho

I have the same issue.  Got the email 2 days ago and tried the code the same day.   Whether I entered it on this site, in game, lower case or upper case I got the same invalid code error.

If it's the yearly promo code that one is quite old (and expired.)

What code are you trying to input?

If its old and expired raid shouldn't be sending it out then.  I too just got an email this week saying to use the yearlygift code for playing for 3 years.