For more information about this gateway, please refer to https://www.propay.com/en-US/Sales-Support/API-Documentation

To add a ProPay gateway, use the following settings:

{
    "cert_str" : "Affiliation Credential for API Access or Disbursement Account Credential for Funds Disbursements (required)",
    "account_num" : "Account Number (required)",
    "term_id" : "ProPay Credential, omit unless directed (optional)",
    "environment_mode" : "External Gateway environment mode. 0 for Live, 2 for Sandbox)"
}