What does 'This cardholder has defaulted' mean?
This response implies that Paystack has tried to charge the customer's card multiple times and it has returned an "insufficient funds" error.
What can I do about it?
Please advise your customer to fund their card and retry the transaction after a 24-hour window. If you're attempting the charge from your end, please advise the customer to fund their card and retry the charge after 24 hours.