The most common reasons:
- The code doesn't apply to what you're currently buying, for example a package code for an add-on service for your release.
- The code isn't valid yet or has already expired.
- The code has already been redeemed as many times as allowed, either in total or per person.
- The code is only intended for a specific account.
- The code was typed incorrectly. Watch out for spaces at the beginning or end.
The message you see when redeeming tells you which reason applies.