Why is the style not being applied to QTableWidjet?

Question

Qt

In the designer itself, everything looks good, but after compilation, the style does not work. Very strange for a newbie in QT, can someone explain? Thank you.

On the left is the compiled application, and on the right is the designer.
Of course, the style does not change anywhere in the code, and I tried to create a new project - the same thing.
The style code itself:
QHeaderView::section {
background-color: transparent;
color: #97A7BF;
font-size: 11px;
font-weight: bold;
}

Answer 1

What if you ask it like that?

tableWidget->horizontalHeader()->setStyleSheet(styleSheet);
tableWidget->verticalHeader()->setStyleSheet(styleSheet);

PS: QTableWidget is slow, learn to use QTableView with models