jasper subreport is not getting printed inside main report

i have mainreport and subreport , where main report is getting printed in jasper, but not the subreport, see below code for subreport

<jr:list xmlns:jr="http://ift.tt/1cl9b3L" xsi:schemaLocation="http://ift.tt/1cl9b3L http://ift.tt/1cl9b3P" printOrder="Vertical">
                    <datasetRun subDataset="customerOrderList" uuid="38a2e0f4-ae87-42ad-b3b4-61853d9a2e23">
                        <dataSourceExpression><![CDATA[new net.sf.jasperreports.engine.data.JRBeanCollectionDataSource($F{customerOrderList})]]></dataSourceExpression>
                    </datasetRun>
                    <jr:listContents height="39" width="590">
                        <frame>
                            <reportElement x="0" y="0" width="590" height="39" uuid="609e3e45-03f6-48d0-8776-e6e393d0dbaf"/>
                            <subreport>
                                <reportElement x="0" y="0" width="590" height="39" uuid="d4ef2aed-7826-49e5-9bb1-7642cbd01279"/>
                                <subreportExpression><![CDATA["src/main/java/com/crafart/reports/customerOrders.jasper"]]></subreportExpression>
                            </subreport>
                        </frame>
                    </jr:listContents>
                </jr:list>

i have debugged the code and see there are no issues in generating the report.

i am passing customer order which contains customer details and list of orders. snippet of my customer bean

public class Customer {
    private String customerName;
    private List<Order> customerOrderList
}

and below code used to generate the report

    List<OrderDeclarationBO> orderDeclarationBOLst = new ArrayList<>();
    orderDeclarationBOLst.add(orderDeclarationBO);
    InputStream in = this.getClass().getResourceAsStream("order.jrxml");
    InputStream jasperIn = this.getClass().getResourceAsStream("order.jasper");
    JasperCompileManager.compileReport(in);
    JasperPrint jasperPrint = JasperFillManager.fillReport(jasperIn, new HashMap<String, Object>(), new JRBeanCollectionDataSource(orderDeclarationBOLst));
    JasperExportManager.exportReportToPdfFile(jasperPrint, "orderInvoice.pdf");

need help, and dont know what is still required to print subreport.

EDIT :- Adding image of the report, where i am getting null values inside sub report, and not aligned properly