Duplex printing on HP laserjet 8000DN

From the time the office F&P servers have been changed to Windows2000 the HP Laserjet 8000DN printer seems to have lost its capacity to do duplex printing. The duplex option is available for the user to select but the “apply” button to apply this change is grayed out and the user cannot select this duplex option.

The drivers were changed, and the Print administrator applies the option to the printer, but the duplex option stays for a few hours and then the option disappears for the user.Is there a fix for this?