The service manuals for the Maxify series of printers are nowhere to be found, but service manuals for other Canon printers list error 6800 as "EEPROM error" with the suggested repair "Part replacement: Replace the logic board ass'y."
Sadly I think the cost of having the logic board replaced by a Canon service centre will exceed the cost of a new printer, meaning the printer from an economical point of view is a total loss. But you could ask about the price before ordering the repair.