Could you run this code and show us the output?
qDebug() << "Initial:" << button1->stylesheet();
qDebug() << "To be set:" << settings.value("stylesheet").toString();
button1->setStylesheet(settings.value("stylesheet").toString());
qDebug() << "After change:" << button1->stylesheet();
qDebug() << "Initial:" << button1->stylesheet();
qDebug() << "To be set:" << settings.value("stylesheet").toString();
button1->setStylesheet(settings.value("stylesheet").toString());
qDebug() << "After change:" << button1->stylesheet();
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