Hello Paul. You may have used a protocol that is not supported by the printer, or set an incorrect queue name if using LPD.
Most printers when they are connected to from Windows use Standard TCP/IP Port > Port 9100. On the Mac, this is called HP Jetdirect-Socket. So, if you haven't tried connecting using this port, then I suggest you add the printer queue again by selecting IP > HP Jetdirect-Socket. Then you can enter the IP address of the printer and search for the appropriate PPD in the Print Using menu.
PaHu