Unable to open ADE 4.5 and epub files

I have a problem with Adobe Digital Editions (4.5.4) in Windows 10.  When I try to open ADE, an icon appears on the taskbar with a blue line (showing it is active), but ADE does not appear on the screen.  This happens however I try to turn it on, e.g. from the start menu, from a screen icon, or by right-clicking on an epub book in 'My Digital Editions' and telling the computer to open it using ADE.  If I try to open an epub (e.g. welcome.epub) and hover over the ADE icon on the taskbar, a thumbnail of the epub appears, but clicking on it just makes the thumbnail disappear.  When I then right-click on the ADE icon and tell it to close the window, a dialog box appears with the message (which I don't understand): "welcome.epub is not open from library, would you like to copy it to library?"  I have tried uninstalling and reinstalling ADE.

Has anyone else had this problem?  How can I get Adobe Digital Editions to open properly so that I can read my epub files?