Sorry, I was very very busy last time.
Yesterday I needed to print. and neither my wifes laptop or my pc would. I took the short way: started up in windows, and put in the driver CD which came with the printer.
did not work
I start to be stressed, I had to print!
Back to my daily AVlinux, and surfed to: HP.com
Yes!!! there was a new version of HPLIP.
Put it on, and within 20 minutes, I could print on both printers and could scan! That was long ago it goes so simple!
Hopefully your pro 8600 is so good supported now with HPLIP!