node.js PDFTron HTML to PDF conversion failed

const { PDFNet } = require('@pdftron/pdfnet-node');

async function main() {
    // Start with a PDFDoc (the conversion destination)
    const doc = await PDFNet.PDFDoc.create();
    const converter = await PDFNet.HTML2PDF.create();

    // add from HTML String data
    converter.insertFromHtmlString(htmlSource);

    // add from a web page location
    //converter.insertFromUrl(webPageLocation);

    // apply conversion
    const page = await converter.convert(doc);

     //doc.pagePushBack(page);
     doc.save('aaa.pdf',PDFNet.SDFDoc.SaveOptions.e_linearized); }
  PDFNet.runWithCleanup(main,licenseKey).catch(function(error) {
    console.log('Error: ' + JSON.stringify(error));
  }).then(function(){ PDFNet.shutdown(); });