Usual "check the contacts- refilling can get messy and I assume you are new to the gig" and with that out of the way onto the good stuff
Printer cartridge manufacturers are unpleasant people and will do just about everything in their power to stop people refilling, tweaking or otherwise depriving them of cartridge sales. The history of such things is long and well documented if you want to look.
I have not dealt with this model (or for that matter Canon in a long time either) so I am afraid I have no definite advice but a quick search for "Canon MP270 cartridge reset" says hold the reset button for 10 seconds (disables checks) and then if it queries it again press the red triangle button (
http://www.extremecow.com/Can_t_print_afte...70-qna1605.html )
The cart probably has an onboard chip which you can reset but that would be tricky and most places that do it tend to opt for a big machine to do the deed rather than say a little switch hidden somewhere on the cartridge.