Does the client have any other listed beneficiaries on their account? The error is from FNB. It looks like they are doing a CDV check for products on the account number. Then it fails hence they are unable to complete the payment. The issue is with the client's bank account/FNB not with EFT secure. We think the BANK account verification FNB does fail. It could be because there are other beneficiaries on the account. Other bank accounts or banks should work.
Note that during the EFT secure payment, if the bank is unable to process payment for any reason, it will fail.