To fix HP DeskJet 2600 offline issue, ensure that both ends of the USB cable are connected to the devices properly. Make sure to connect the Ethernet cable properly if you are using a network printer and check the HP DeskJet 2600 Ink cartridges. Then, establish a connection between the printer and the computer correctly and check the internet connection if you are using a wireless printer. Use a different cable and ensure that it is not the fault of the cable. In case you are using a wireless or network printer, then try to connect the printer to your computer via a USB cable to confirm that your printer is functioning correctly to get the issue of HP DeskJet 2600 offline resolved.