Perhaps you’re simulating:

Rather than PIE - Play in Editor. Widgets do not show up while simulating. Another reason would that there are no visible elements in the widget or the render opacity of the root / vital elements is set to 0.
Perhaps you’re simulating:

Rather than PIE - Play in Editor. Widgets do not show up while simulating. Another reason would that there are no visible elements in the widget or the render opacity of the root / vital elements is set to 0.