受益人账户格式正确，但已关闭，无法再接收资金。
AC04 means the IBAN is structurally valid and was once a real account, but the account has since been closed. The beneficiary may have changed banks or closed the account deliberately.
Contact the beneficiary and ask for their current active account details. Update your payment records and resend once you have the new IBAN.
联系受益人，获取其当前有效的账户和IBAN，用新信息重新汇款。
Track your payment by UETR — free on Ohmyfin: SWIFT 追踪器
→ Full AC04 reference (English)