Hello. I am running Vaadin 8 and Version 2.0.2 I created Grid gridAgentCo

Hello.
I am running Vaadin 8 and Version 2.0.2
I created Grid
gridAgentContractList = new Grid();
gridAgentContractList.addColumn(AgentContractMainInfoDTO::getAgentContractId).setCaption(“Id АД”).setWidth(80).setId(“agentContractId”);
gridAgentContractList.addColumn(AgentContractMainInfoDTO::getAgentContractNumber).setCaption(“№ АД”).setWidth(80).setId(“agentContractNumber”);
gridAgentContractList.addColumn(AgentContractMainInfoDTO::getSubjectName).setCaption(“Наименование Агента”).setWidth(300).setId(“subjectName”);
gridAgentContractList.addColumn(AgentContractMainInfoDTO::getBlock).setCaption(“Блок АД”).setWidth(300).setHidden(true).setHidable(true).setId(“block”);
gridAgentContractList.addColumn(AgentContractMainInfoDTO::getFilial).setCaption(“Филиал АД”).setWidth(300).setHidden(true).setHidable(true).setId(“filial”);
gridAgentContractList.setSelectionMode(Grid.SelectionMode.MULTI);
gridAgentContractList.setVisible(false);

	and   gridAgentContractList.setItems(listAc);
	
	When I tried to export to grid. I got empty Excel
	
	
    Button downloadAsExcel = new Button("Download As Excel");
    StreamResource excelStreamResource = new StreamResource((StreamResource.StreamSource) () -> {
        return Exporter.exportAsExcel(gridAgentContractList);
    }, "my-excel.xlsx");
    FileDownloader excelFileDownloader = new FileDownloader(excelStreamResource);
    excelFileDownloader.extend(downloadAsExcel);
	
	
	Why I have empty Grid. Can you help me?(((((