In a nutshell, a 'Do Not Honour' error code comes up when the customer's card issuer is refusing to send an authorisation token back to your payment system. It's not necessarily anyone's fault; the issuer simply didn't validate the transaction.

What it means to be honored?

If someone is honored, they are given public praise or an award for something they have done. It's nice to be honored with an award like this. 4. singular noun. If you describe doing or experiencing something as an honor, you mean you think it is something special and desirable.

Can I not honor SBI debit card?

The DO NOT HONOR or Invalid Service Code messages indicate that the customer's card-issuing bank or the payment processor declined the transaction. ... After obtaining the verbal authorization, you can capture the transaction manually. If you choose not to capture the transaction, no further action is required.