Based on my attempts to get WinSCP to work (as it has for years and years) the only thing that I can think of is that a recent update to Windows 10 has broken WinSCP.
Some of the attempts are show in this screenshot video:
First, the WinSCP window opened partially off my display, but I could not maximize or move it to the display to work with it. I could click on the toolbar and see my list of sites. Clicking on one the "master password" dialog opened and accepted the password, but the window never appeared.
Using "alt-tab" I can see WinSCP preview boxes, but selecting them does not bring up the window. Using Win-tab no window shows up on the desktop.
I had to use TaskManager to kill the app. Restarting it I could see a "Update" window preview from the taskbar, but as before could not open any winscp window on the display.
Here are things I have tried to get around this (none of them worked):
-Restart my laptop
-Disconnect my laptop from external displays so only the internal screen is displaying
Attempt to install the update by downloading through a browser. This failed because the .exe file could not be overwritten
Uninstalled WinsSCP. Reinstalled current version. Still failed
Installed a previous version that I know used to work.
Cleared up space on my harddrive which was getting full.