Resetting a chip that isn't "locked" can sometimes cause errors. Wait until your Canon printer displays "Toner Low" or "Replace Toner."
Why? Because while you physically added toner, the electronic chip on the side of the cartridge still thinks it is empty. It has reached its programmed page count limit and has "locked" the cartridge as depleted. The printer is blind to the powder inside; it only listens to the chip. Canon 337 Toner Chip Resetter
That said, to protect yourself:
Place the cartridge onto the resetter so that the chip’s gold contacts align perfectly with the pogo pins on the resetter. Some resetters have a tray; others require you to hold the cartridge firmly. Resetting a chip that isn't "locked" can sometimes