Initially, check the Printer list on your computer to ensure that your printer is connected to your computer. Then, restart the printer and wait for the printer to become idle. If the connection is not restored after restarting your printer, restart your router also. Finally, connect all the devices and try to print.
Here are instructions to fix the hp 2600 printer offline. Manual to Change the USB Connection.
Network printer connection.
Reset the printer. Check whether the printer is idle without any sounds before starting. Disconnect the power cord from the rear of the printer. Unplug the power cord from the wall outlet. Wait for a few minutes.