The window is probably off the screen. Hover the mouse over the N1MM+ icon
on the Windows task bar. You should see more than one miniature window just
above the task bar. One of them will be the Digital Interface window.
Right-click on it, select Move, press one of the arrow keys on your
keyboard a couple of times, and the window should appear. You can move it
with the mouse and mouse-click when you have put it where you want it.
Or, you can shut down N1MM+, open the N1MM Logger.ini file, look for the
section called [DigitalInterface1], and in that section find the line
Left=xxxx and change it to Left=0, find the line Top=xxxx and change it to
Top=0, save the ini file and once that is done, start N1MM+. The DI window
should now be at the top left corner of the screen.