We have just inherited a nice HP DesignJet T770 44" plotter, and it was a piece of cake to get it up on our network and get on the web admin page. However, I can't print to it at all. That is no error from multiple computers that I have installed the driver on, but print jobs never come out.
The only thing I can think off is that because the plotter has sat for a while, most of the ink cartridges are saying "Out of warranty" and a yellow warning icon shows on the status display. According to HP, this is supposed to prevent the plotter from being used to prevent "damage to the device" (read: damage to HP's bottom line because they want to force you to buy new ink even if yours is perfectly fine).
So, after a bunch of research, this page HP Inkjet Supplies - Ink Expiration mentions that the T770 can override the ink expiration warning,...