HP 310X - Manual (Page 144)

Is the USB light ON solid green?
for HP Jetdirect 175x external print server/Internet connector for USB
and HP Jetdirect 310x external print server/Internet connector for
USB
USB port
USB light
Check the USB light on your print server. It should be ON solid
green (bright green in color and glowing continuously, not blinking).
If it is not ON solid green, please follow the troubleshooting steps
below.
Make sure that you have a USB cable connected between your
printer and the USB port on the print server. It should be a
standard USB A-to-B cable, like this:
to print server to printer
Note that the print server does not support parallel-to-USB
converters (for connecting a parallel printer to a USB host) -- it
1.