I have an HP 4000 Series PCL 5e printer going across a network. I am using our domain controller as a print server. I have a duplexer installed on this printer. I have turned the duplex option to "on" in the printer configuration. Whenever I go into the printer driver on the server and try to click the dupex checkbox under the config tab it will not let me click apply. When I click OK it just unchecks the box. I can't figure out how to get this printer to print in duplex mode. Is there something I am missing?