Please note that when processing payments through the Electronic Bank Payment bundle, and you encounter Processing Error EP_00015, there are possible explanations for this error message, this includes but not limited to the following:
1) The account used by the bank does not include the subsidiary of the transaction.
The solution would be to select the subsidiary of the transaction on the account record.
2) The vendor is set to inactive.
The solution would be to re-activate the vendor
3) The preferred bill payment form has a custom mandatory field on it.
The solution would be to set to uncheck this field on the preferred bill payment form (Customization > Forms > Transaction Forms)
You refer to SuiteAnswers Article ID 76759 for more information.