setWindowState(Qt.WindowMaximized) does not work anymore

import sys
from PySide6.QtCore import Qt
from PySide6.QtWidgets import QApplication, QMainWindow, QPushButton

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("My App")
        self.setWindowState(Qt.WindowMaximized)  # comment out/in for success/failure
        button = QPushButton("Press Me!")
        self.setCentralWidget(button)

app = QApplication(sys.argv)
window = MainWindow()
window.show()
app.exec()