This is an umbrella bug for cases where a display is reconnected or woken from sleep and - The display is still enabled in Display Configuration - plasmashell acts as if the display is detected and enabled (panels and windows aren't moved to another display) - You can move the mouse cursor to the display but not see it (if you can see the mouse cursor, that's a different bug in containment or a display driver) This affects single and multiple display setups, X11 and Wayland