Detach the USB cable from the Mac and reattach it before attempting to fix the HP 2600 Printer Offline. The printer should then be turned off, followed by some waiting. Next, switch on the printer after a short while. The early phases of printing the papers may involve some noise from the printer. The printer needs to be off and silent prior to beginning. Further, after a little while, reattach the USB cable. Wait until it is finished printing if the printer starts to do so.