The response code 91 appears when swiping the card, indicating that the card issuer or UnionPay cannot operate. It is used to indicate that the transaction was rejected due to the error of the card issuer (or UnionPay), such as the following situations:

1. The card issuer (or the transfer-in/transfer-out party) is not operating normally

2. The card issuer (or the transfer-in/transfer-out party) is abnormal but has not signed an authorization agreement with the UnionPay processing center Agreement

3. The card issuer (or the transfer-in/transfer-out party) signed out or failed to sign in

4. The card issuer (or the transfer-in/transfer-out party) has an invalid operating status

5. The card issuer (or transfer-in/transfer-out party) is closed by the UnionPay processing center

6. The card issuer (or transfer-in/transfer-out party) line is abnormal

7. The internal system of the card issuer (or transfer-in/transfer-out party) times out

You can call the card issuer or UnionPay and then try again.