When trying to plot using AutoCAD Lt, 2013 (Windows 7) on my HP DesignJet 500 42, I can't select the plotter from the list. It is shown on the printer list but when I choose it, the selection returns to "None". This, even if I make the plotter the default printer in Windows and in AutoCAD options settings. I am able to print to it using other applications. Why is it doing this?