The daemon couldn't open the printer device. This can happen
for several reasons (e.g., the printer is offline or out of paper,
or the paper is jammed). The actual reason depends on the meaning
of error codes returned by the system device driver; some printers
can't supply enough information to distinguish when a printer
is offline or having trouble, especially if connected through a
serial line.
Another possible cause of this message is that some other
process, such as an output filter, has an exclusive open on the
device: all you can do in this case is kill off the offending program(s)
and restart the printer with
lprc.