With the Deskjet D1420 disconnected, hp-probe finds no USB printers (duh). With the Deskjet D1420 connected, hp-probe finds it. hp-testpage produces error: Unable to communicate with printer Deskjet-D1400-series. Please check the printer and try again.
Note that hp-probe found it.
hp-testpage also produces a popup saying ... There is a problem with a print cartridge (1017)
It does not say which one or why this would cause communication failure.
How do I figure this out?