1. Open the canon ip2770 case
2. Release all cartridge
3. Lift the printer upside down
4. O'clock to get out the dirt in the printer
5. Plug the cartridge and try to turn on the Canon 2770
6. If error still appear, please to disassemble the roller and find the dirt that clog rotation and clean up.
I hope this article will be help you. This step i prove and succes