do_not_honor
Do not honor. The issuing bank declined without explanation. It's one of the most common codes and usually reflects the bank's internal risk rules.
Will retrying the charge work?
Sometimes. Retry a couple of times over several days, but email the customer in parallel.
What to do about it
Space out retries over a week and ask the customer to contact their bank or switch cards. Repeated rapid retries can make issuers more suspicious.
What to tell your customer
Your bank declined the payment. Contact them to approve the charge, or update to a different card.