Restarting your printer and opening Run will fix the Canon Printer Offline error. In the control panel, select Device and Printers. Choose See what's printing from the context menu when a green checkmark shows when you right-click on the icon. Instead, right-click on your printer and select Set as Default Printer if it is gray. At last, turn off the two boxes next to Use Canon Printer Offline and Pause Printing if you notice them by pressing the printer.