The Simulator remembers the screen layout in a configuration file and the chart windows will be positioned accordingly when you start the Simulator next time. If this configuration file is damaged or lost, the charts may become invisible in the Simulator.
the Simulator to reset the screen layout, just check one more interval
in the top of the Simulator window when you start the Simulator. Then
press Start. The windows should be visible again after that.
can stop the Simulator, start it again, and uncheck the interval you added,
in order to get your old chart setup back.