Every once in a while, when the Multiplicity window (showing the screen of a Secondary PC) is minimized, the window itself disappears... as does the taskbar 'bar' of it, making it impossible to get to it.
I have had to open up the Task Manager, select the Multiplicity window item in it, and select Move To Front to get it back.
Sometimes (I think), somehow, it shows up without doing that.. probably in the same mysterious way it disappeared.
Not sure what the trigger is on that. It just randomly happens, so when it does, it's already too late to investigate what triggered it. But, I'll post here if I find any further clues. I never really notice the taskbar 'Multiplicity bar' disappearing... I just eventually notice (after working with some other open windows) that the Multiplicity window is no longer there, when I want to go back to the Secondary PC.
I'm not even sure it only happens when minimized. I THINK it has happened even when I just put some other window fullscreen, or maybe even just to the front/focus. Again, I'll have to try and isolate the trigger somehow.
But, if it happens to anyone else, just go into the Task Manager to solve it, as outlined above.