when using word on a dual screen, and it's maximized there could be a problem when you try to restore the window.  After restoring it, the screen fully disappears.

The solution for this is very easy : after restoring the window, choose the option move.  use your keyboard arrow keys to move it around.  Even when you don't see the blue bar as it seems off the screen, at a certain moment you should be able to bring it back on your screen.