Have you taken out the cartridge and re-inserted again?
If so and you still have the problem try:
1. On your screen, locate and click the Start button. From the Start menu, click Shut Down. In the Shut Down Windows dialog box, select Restart the computer, then click Yes. Turn off peripherals, as well.
2. Unplug the printer from the power source.
3. Unplug the printer from the computer.
4. Wait two minutes.
5. Plug the printer into a power outlet on a surge protector or wall outlet.
6. Plug the printer cord into the computer. Do not use an extension cord for this connection.
7. Turn on the computer.
If the steps above do not resolve this issue, this product is fully supported by Canon. Please contact Canon support at (757) 413-2848 for further troubleshooting.