According to the service manual error code 6800 means that "A problem occurred in reading from or writing to the EEPROM". The suggested parts replacement is the logic board. See page 12/64 in the service manual.
I think that turning the printer off and disconnecting power for some minutes and then reconnecting power and turning on the printer doesn't make the error go away?
I don't know if clearing the EEPROM from service mode will remove the error, but you lose the printer history and absorber counter value in doing so. You might also have to uninstall and reinstall the printer to get the display language back to English. Probably the logic board error will prevent the printer from starting, so no service mode operations will be possible?
Thank you for your very detailed response. I have a working MP560, and I bought this used one hoping I would have another working MP560. This one with the error has a set of OEM cartridges I can use. I was thinking I should clean the print head, but I should not try the head in the working printer. I will just box up the head with a note about its unknown use. Any other ideas anyone might have, let me know.
Al