Not sure how to explain this but I have seen this in other windows apps that save the window position. I think it happens more with fsuipc 7 is moved to another monitor. In the ini, there is a value called window with a x,y,xd,yd, where x, y are the upper left corner position and xd yd are the horizontal length and vertical length. Normally this is something like 500,500, 1000, 800. So when I choose show from the icon, fsuipc shows normal. However sometimes when the program is closed the window values are saved -5000, -3000, 1000,800. So when show is selected to display main window of fsuipc it cannot be seen. So I close everything and edit the ini window values. 100,200,800,600. That fixes it. I move and resize the program and then exit to save the position.
this has happen since day one and was just waiting to see if it fixes itself. They update to windows build 20h2 broke it again. I would see a way to show the fsuipc 7 application with a default position although not to edit the ini file.