I meet the problem, so I take a test at MainWindow, the problem remains the same.
Here is the code in “MainWindow::MainWindow(QWidget *parent)…”
QToolButton* bt = new QToolButton(this);
bt->setIcon(QIcon(":/te.png"));
bt->setToolButtonStyle(Qt::ToolButtonIconOnly);
bt->show();
It looks like:

My resource file is like this:

You have given the icon an alias
tebut called the icon by it’s full namete.png. Use:/teinstead.