What does Do Not Honour (05) mean?

Do not Honor (05) is the most common and general message for card transactions that are declined by the Bank. It indicates that the Issuing Bank will not validate the transaction. It is caused by many factors such as mistyping, insufficient funds, etc.
To resolve this, customer needs to contact the Issuing Bank and tell what had happened. Once the problem is solved, customer should be able to transact.