Export to Excel button doesnt work

I am evaluating smartGWT (v 4.0) for our company. I am at present using the evaluation copy with full features enabled.
As part of export to excel functionality I dont get any error in the logs but just that nothing happens on the browser when the export to excel button is clicked.

Here is the relevant part of the code

IButton exportToExcelButton = new IButton("Export");
exportToExcelButton.addClickHandler(new ClickHandler() {

@Override
public void onClick(ClickEvent event) {
String exportAs = (String)exportForm.getField("exportType").getValue ();

FormItem item = exportForm.getField("showInWindow");
boolean showInWindow = item.getValue() == null ? false : (Boolean)item.getValue();

DSRequest dsRequestProperties = new DSRequest();
dsRequestProperties.setExportAs((ExportFormat)Enum Util.getEnum(ExportFormat.values(), exportAs));
dsRequestProperties.setExportDisplay(showInWindow ? ExportDisplay.WINDOW : ExportDisplay.DOWNLOAD);

supplyItemGrid.exportData(dsRequestProperties);

}