The error "Processing error. -19 Authentication failed" occurs most often because the card issuing bank refused the transaction. Banks have various policies based on: payment amount, type of card: business or not, if the card is enrolled in 3DSecure or not, if the shop is offshore or not etc.
Even if you have been able to successfully complete a transaction recently, the bank may still refuse your payment based on their policy. In order to find out more information about the reason payment fails you must contact your bank.