Use C++ to export svg error

I export svg with COM interface in C++. Hear's my codes:

try
{
app->Visible = VARIANT_TRUE;
VGCore::IVGDocumentPtr doc = app->ActiveDocument;
if (!doc)
{
QMessageBox::warning(nullptr, tr("No active document"), tr("No active document in CorelDRAW!"));
return nullptr;
}

qDebug() << "selection count:" << doc->Selection()->Shapes->Count;
VGCore::cdrExportRange range = VGCore::cdrExportRange::cdrCurrentPage;
if (doc->Selection()->Shapes->Count > 0)
{
range = VGCore::cdrExportRange::cdrSelection;
}

tmpSvgFilename = utils::createUUID() + ".svg";
tmpSvgFilename = tmpDir.absoluteFilePath(tmpSvgFilename);
//QString tmpSvgFilename("d:/tmp.svg");

qDebug().noquote() << "export corel draw active document to" << tmpSvgFilename;

VGCore::IVGStructExportOptionsPtr opt = app->CreateStructExportOptions();
VGCore::IVGStructPaletteOptionsPtr pal = app->CreateStructPaletteOptions();
opt->AntiAliasingType = VGCore::cdrNormalAntiAliasing;
opt->ImageType = VGCore::cdrRGBColorImage;
opt->ResolutionX = 72;
opt->ResolutionY = 72;
pal->PaletteType = VGCore::cdrPaletteOptimized;
pal->NumColors = 16;
pal->DitherType = VGCore::cdrDitherNone;
VGCore::ICorelExportFilterPtr filter = doc->ExportEx(typeUtils::qStringToBstr(tmpSvgFilename), VGCore::cdrSVG, range, opt, pal);
if (filter->HasDialog)
{
if (filter->ShowDialog(0))
{
hr = filter->Finish();
if (FAILED(hr))
{
qDebug() << hr;
QString errorMessage = QString::fromLocal8Bit(std::system_category().message(hr).c_str());
qWarning() << errorMessage;
}
}
}
}
catch (_com_error& ex)
{
//QString errorMsg = (LPTSTR)ex.ErrorMessage();
//wprintf(L"Error occurred: 0x%08X (%s)\n", ex.Error(), ex.ErrorMessage());
QString errorMessage = QString::fromLocal8Bit(std::system_category().message(ex.Error()).c_str());
qDebug() << errorMessage;
}

And I got an error information: "The remote procedure call failed."

How to fix this error. Thanks.