Here are some possible reasons:
• Bonus cannot be used with your current payment method. To use it, pay with a card or Alipay Balance.
• Bonus cannot be used when your payment currency is not the same as the bonus currency.
• Bonus cannot be used on virtual items or services, such as gift cards, E-tickets and mobile top up services.
• Bonus has expired. To check the bonus expiration date, go to the Bonus page in Alipay.