This error pops up when a payment has been declined at the gateway’s end because one of the filters at the Fraud Detection Suite has been triggered. 

Remember: ‘E00027’ is thrown up irrespective of which filter has vetoed the payment (it is also thrown when form fields are marked as required), but Authorize.Net will send you an email with details on which filter was triggered. You can also check with the Authorize.Net web interface for specifics and reports on which filter stopped the payment from going through at Reports >> Transaction Detail Reports or Search >> Suspicious/Unsettled transactions