JasperserverRestClient

Good evening I'm using JasperserverRestClient to retrieve a jasper server report, but when I try to use ReportExecutionDescriptor it's null.

Could anyone help me?

RestClientConfiguration configuration = new RestClientConfiguration("https://xxx/jasperserver");
        JasperserverRestClient client = new JasperserverRestClient(configuration);
        Session session = client.authenticate("xxx", "xxx");

        ReportExecutionRequest request = new ReportExecutionRequest();
        request.setReportUnitUri("/rest_v2/reports/sistemas/guia_tiss/spsadt");
        request.setAsync(Boolean.FALSE);
        request.setOutputFormat(ReportOutputFormat.HTML);  

            OperationResult<ReportExecutionDescriptor> operationResult = session.reportingService().newReportExecutionRequest(request);
        ReportExecutionDescriptor reportExecutionDescriptor = operationResult.getEntity();