QPrintDialog does not return a printer

my code, which has not been modified, worked with qt-5.9.1

QPrintDialog appears and I select a printer, but the log file shows:

check for printer
result:1
page 767 x 1110
Could not determine printer to print to

My code is:

QtPdf::QtPdf(const RptType tp, const short id)
{
QString fn = QDir::homePath() + "/reports/doc-";
fn += QString::number(id) + ".pdf";
printer.setOutputFileName(fn);
printer.setDocName("Invoice");
printer.setColorMode(QPrinter::Color);
printer.setFontEmbeddingEnabled(true);
QPageLayout qpl;
printer.setOutputFormat(QPrinter::PdfFormat);
printer.setPageLayout(qpl);
printer.setPageOrientation(QPageLayout::Portrait);
printer.setCreator("xyz SCRL");
QPrintDialog *dialog = new QPrintDialog(&printer);
dialog->setWindowTitle("Print Document");
if (dialog->exec() != QDialog::Accepted)
return;
dY = BORDER_TOP;
painter.begin(&printer);

QFont qf;
qf.setFamily(DEFAULT_FONT);
painter.setFont(qf);

QRectF pz = printer.pageRect(QPrinter::DevicePixel);
pageHeight = pz.bottom();
pageWidth = pz.right() - pz.left();
cout << "page " << pageWidth << " x " << pageHeight << endl;
getCoy();
SetFontSize( 10 );
switch (tp) {
case invoice: getInv(id); break;
case reminder: remind(id); break;
}
}