A. 1. Ensure the promo code is valid: Double-check the expiration date and terms of the promo code. 2. Clear the app cache: Go to Settings > Apps > Spirit Airlines > Storage > Clear Cache to remove any corrupted data. 3. Restart the app: Close the app completely and reopen it to refresh the session. 4. Try entering the promo code at checkout: Make sure you are entering the code in the correct field during the payment process.

B. 5. Use the website: If the app does not allow you to enter promo codes, try booking through the Spirit Airlines website.