Este debería ser el flujo más sencillo de realizar, simplemente iniciamos el proceso de pago y capturamos las imágenes asociadas, no olvidar activar el modo de debug y el log de wordpress para poder rescatar los logs necesarios para la certificación.

  [04-Dec-2015 19:27:07 UTC] [API]    -> ENTRANDO HANDLER
  [04-Dec-2015 19:27:07 UTC] [API]    -> ENTRANDO HANDLER DEBIDO A POST POR EL FORM
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> Iniciando WSPOST
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> SE INTENTA PAGAR LA OC : 434
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> MONTO A PAGAR : 22990
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> TIPO DE TRX  TR_NORMAL_WS
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> ID SESION 20151204072707
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> CODIGO DE COMERCIO : 597020000174
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> Doble Validación Desactivada / pending
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> SUCCESS: (FINAL URL) http://www.pandora.cl/wc-api/WC_Gateway_WebpayplusWS/?&FINAL=434
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> SUCCESS: (RETURN URL) http://www.pandora.cl/wc-api/WC_Gateway_WebpayplusWS/?&RETURN
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> INICIANDO EL PROCESO DE CONEXIÓN CON TRANSBANK
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> ASIGNANDO DATOS
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> GENERANDO EL WEBSERVICE
  [04-Dec-2015 19:27:07 UTC]     -> Servidor : 0
  [04-Dec-2015 19:27:07 UTC] [CW]    -> CERTIFICACION : 0 https://webpay3g.orangepeople.cl/WSWebpayTransaction/cxf/WSWebpayService?wsdl
  [04-Dec-2015 19:27:07 UTC]     -> Generando Webservice con URL : https://webpay3g.orangepeople.cl/WSWebpayTransaction/cxf/WSWebpayService?wsdl
  [04-Dec-2015 19:27:07 UTC] [CW]    -> WebService Creado exitosamente
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> WEBSERVICE CREADO EXITOSAMENTE
  [04-Dec-2015 19:27:07 UTC] WebpayService Object
  (
  [soapClient] => MySoap Object
      (
          [useSSL:MySoap:private] => 1
          [KEY:MySoap:private] => /var/www/wp-content/plugins/woocommerce-webpayplus-webservice/llaves/597020000174.key
          [CERT:MySoap:private] => /var/www/wp-content/plugins/woocommerce-webpayplus-webservice/llaves/597020000174.crt
          [debug:MySoap:private] =>
          [trace] => 1
          [_classmap] => Array
              (
                  [getTransactionResult] => getTransactionResult
                  [getTransactionResultResponse] => getTransactionResultResponse
                  [transactionResultOutput] => transactionResultOutput
                  [cardDetail] => cardDetail
                  [wsTransactionDetailOutput] => wsTransactionDetailOutput
                  [wsTransactionDetail] => wsTransactionDetail
                  [acknowledgeTransaction] => acknowledgeTransaction
                  [acknowledgeTransactionResponse] => acknowledgeTransactionResponse
                  [initTransaction] => initTransaction
                  [wsInitTransactionInput] => wsInitTransactionInput
                  [wpmDetailInput] => wpmDetailInput
                  [initTransactionResponse] => initTransactionResponse
                  [wsInitTransactionOutput] => wsInitTransactionOutput
              )
          [_soap_version] => 1
          [sdl] => Resource id #28
      )
  )
  [04-Dec-2015 19:27:07 UTC] [WSPOST]    -> INICIACNO EL INIT TRANSACTION :
  [04-Dec-2015 19:27:07 UTC] wsInitTransactionInput Object
  (
  [wSTransactionType] => TR_NORMAL_WS
  [commerceId] => 597020000174
  [buyOrder] => 434
  [sessionId] => 20151204072707
  [returnURL] => http://www.pandora.cl/wc-api/WC_Gateway_WebpayplusWS/?&RETURN
  [finalURL] => http://www.pandora.cl/wc-api/WC_Gateway_WebpayplusWS/?&FINAL=434
  [transactionDetails] => wsTransactionDetail Object
      (
          [sharesAmount] =>
          [sharesNumber] =>
          [amount] => 22990
          [commerceCode] => 597020000174
          [buyOrder] => 434
      )
  [wPMDetail] =>
  )
  [04-Dec-2015 19:27:07 UTC]     -> PRIVATE KEY /var/www/wp-content/plugins/woocommerce-webpayplus-webservice/llaves/597020000174.key
  [04-Dec-2015 19:27:07 UTC]     -> CERT KEY /var/www/wp-content/plugins/woocommerce-webpayplus-webservice/llaves/597020000174.crt
  [04-Dec-2015 19:27:09 UTC] [WSPOST]    -> initTransaction sin problemas. Continuamos...
  [04-Dec-2015 19:27:09 UTC] [WSPOST]    -> GENERANDO LA RESPUESTA EN XML
  [04-Dec-2015 19:27:09 UTC] [WSPOST]    -> VALIDANDO CONTRA CERTIFICADO
  [04-Dec-2015 19:27:09 UTC]     -> Servidor : 0
  [04-Dec-2015 19:27:09 UTC]     -> SERVER CERT  : 0 /var/www/wp-content/plugins/woocommerce-webpayplus-webservice/llaves/certificate_server.crt
  [04-Dec-2015 19:27:09 UTC] [WSPOST]    -> OBTENIENDO RESULTADO DE VALIDACION
  [04-Dec-2015 19:27:09 UTC] [WSPOST]    -> VALIDACION CORRECTA
  [04-Dec-2015 19:27:09 UTC] wsInitTransactionOutput Object
  (
  [token] => ec8dc1ee11480f42c111f664fc0905410d16d2a8268767d1677743eeb3bd7b8e
  [url] => https://tbk.orangepeople.cl/filtroUnificado/initTransaction
  )