I've lost two printers that displayed a message that indicated that carts were not correct when in fact they were the correct ones. Initially it displayed it and then on reinsertion it went away only to appear again at a future date and then totally not recognizing the correct cartridges....even brand new OEM ones. It was not the printhead but the logic board. The two that went this way was an MP970 and and MP980.
Now here's the interesting part. Both printers had been fine, put away for a few months and then the problem surfaced on using it again. Recently something similar came up with an iP6600 that indicated that the wrong printhead was installed....of course not. But the message went away after it was left sitting powered up for a few hours. This machine had been stored for about 6 months.
Does that mean that Canon printers cannot be stored.. no not at all. Something happens to "some" that are brought out of storage.. What it is I don't know. A mystery and will probably remain so.