Duplex printing does not work

[Malte Gell]

Hi there,

I just attached a duplex unit to my HP DeskJet 920C but it does not work.

System:
openSUSE 10.3
Cups 1.2.12
hplip-hpijs driver 2.7.7

I use the HPLIP backend, in

/etc/cups/ppd/deskjet920c.ppd

I have set

*DefaultDuplex: DuplexNoTumble

but, nevertheless it does not work. When I print somethin, e.g. from OpenOffice the 920C still uses two papers instead of printing on the back of paper one...

Thanks for any hints where to start to dig...
Malte