A rejected code almost always comes down to one of four fixable causes. The most common is an entry error: the code entry field is case sensitive, so a stray space or lowercase letter will fail. Fix it by retyping the code character by character, or pasting it from the promotion page to avoid typos.
Ineligibility is next. Codes are typically limited to new players, one claim per person, household or IP address, and some offers exclude certain countries or payment methods. Check your player status and the promotion's eligible-countries list before retrying. Expiry is another frequent culprit: codes carry campaign dates, and one that worked last month may no longer be live. Trust the promotion page's current validity window rather than an older forum post.
Finally, a missed claim step: some offers require the code before the deposit confirms, not after, and others need an explicit opt-in. Follow the offer terms' order of steps, then make a fresh attempt once each one is confirmed. If all four checks pass and the code still fails, a quick message to support usually resolves it within minutes.