Problem with PySide6 and QToolButton

1

I developed an app under Windows with PySide6 that works well, except …:

In my toolbar I want a button that opens a short submenu, where you can activate or deactivate some options. The button is shown in the toolbar but the submenu doesn’t open. What’s wrong ???

...
        MenuAnsicht = QMenu()
        self.MenuAFav = QAction("Favoriten")
        self.MenuAFav.setCheckable(True)
        self.MenuAFav.setChecked(True)
        MenuAnsicht.addAction(self.MenuAFav)
        self.MenuARoP = QAction("Receiver ohne Pay-TV")
        self.MenuARoP.setCheckable(True)
        MenuAnsicht.addAction(self.MenuARoP)
        self.MenuARmP = QAction("Receiver mit Pay-TV")
        self.MenuARmP.setCheckable(True)
        MenuAnsicht.addAction(self.MenuARmP)

        tbtnAnsicht = QToolButton()
        tbtnAnsicht.setFixedSize(50, 35)
        tbtnAnsicht.setToolTip("Ansicht")
        tbtnAnsicht.setIcon(QIcon(".\\icons\\iconAnsicht.png"))
        tbtnAnsicht.setPopupMode(QToolButton.ToolButtonPopupMode.MenuButtonPopup)
        tbtnAnsicht.setMenu(MenuAnsicht)

        toolbar.addWidget(tbtnAnsicht)
...