Hmmm ... that's a relatively new printer, I think. Bummer.
* Very helpful attachment. I wish more people did that.
* Anything change between when it worked, and stopped working?
* How long had it been since the printer was working ok? If more than a week or so, is it your practice to do "nozzle checks' about weekly to reduce clogging?
* Is the "nozzle check" ok? That always should be the first step when problems turn up. The risk is a fried print-head if you keep printing with clogged nozzles or ink starvation.
* It can be Very Helpful to attach a scan of the nozzle check, if possible.
* If nozzle check not ok, refrain from almost any other printing until resolved.
* Have you tried "normal cleaning"? Did that help? How about "Deep Cleaning" with over-night delay between another nozzle check?
* Try removing and replacing the print-head, then another nozzle check.
* If the printer is still under warranty, I'd ask Canon tech support about whether it is ok to do a print-head alignment. My experience with Canon has been mostly very positive, but YMMV.
* I hope I'm wrong, but I don't think a print-head alignment will help.
* BTW, what your printer is doing isn't really "banding". That's more of a software issue, typically with Photoshop and too much manipulations with 8-bit per channel images.