I was using qt5 with soqt1.6.0. Then I updated qt version to 6.5.2 and soqt to 1.6.2. After that I have seen a bug in my application.
SoQt FullViewer has a method called addAppPushButton(QWidget*); and I am giving my QPushButtons to this method to place them at the left side of the 3d viewer at the top of the rotation wheel. In the previous version, the buttons were clickable, but now buttons cannot be clickable.

Actually, buttons are previously owned by another widget inside a vertical layout. When I use addAppPushButton, they are added to the left side of the view. After the qt update it makes buttons unclickable