This has happened three times now. It works one day and then the next is gone.Can you be more specific? In the latest APCC, the Emergency Slew window closes when a slew completes. So, do you mean the window dowsn't open at all? If that is the case, then maybe another window is hiding it?
Or, if you "Save Window Positions" enabled and have multiple monitors, maybe it is being saved off screen? Or maybe it was saved in the minimizing state? Usually, turning off "Save Window Positions" in APCC's Settings menu will handle these cases.