There's a basic difference between Epson's electro-mechanical piezo nozzles and Canon's electro-thermal bubble-jet nozzles, whose modus exodus is generally that of burnout (electrical shorting), and is not reversible. Having gone through four iPF heads in the past 7 years, none of the nozzle failures have been reversible on cleanings. A Canon tech once told me that if a single cleaning doesn't reverse it, more are just wasted ink and a new head is needed.
Canon's heads have a huge nozzle redudancy and auto-remapping of failed ones. Seems you have reach the point that this can no longer compensate, and a new head is needed. The problem of trying to force printing in spite of printhead error messages is that of drawing too much current through the too many shorted nozzles, with rising head temps - further failures, and a blown controller board possibly resulting.
Canon have been generous in out-of-warranty head replacements in some cases. How old is the printer, and how many sq. ft. or meters have you printed?
Pete