Canon makes a line of colour all-in-one printers called Pixma, which have a P before the model number. For a variety of reasons, including using recycled or refilled ink cartridges, the printer will sometimes tell you that the ink is low even if it's not. If you want to override this message, you can do so within about 10 minutes depending on the problem. Keep going through the various troubleshooting options until something works.
Turn the printer off, then on again. When the "low ink levels" message pops up on the LCD screen or your computer, click "OK" and move on. If you don't mind seeing this message, you can continue to do this whenever you restart the printer. You'll still be able to print as usual.
Open the top of the printer via the handle on the front and locate the ink cartridges. Grip the front and back and pull straight up to remove any that the printer thinks are low. Look at the bottom for the rows of copper squares. Put a thin strip of tape on the top row and put it back in the printer. Close the lid, wait for the error message, and open it again. Remove the cartridge and add an additional piece of tape over the next row down. Then put it back in, close the lid, and wait for the error message. Remove the cartridge once more and take off the tape, then replace it. This essentially "tricks" the printer into thinking it's a new cartridge. Repeat with any other cartridges showing error messages.
Remove the cartridges and rub the bottoms as well as the bottom of the ink tray with a paper towel dampened with rubbing alcohol. This will remove any clumps of dried ink that can block the ink from flowing or the cartridge from communicating with the printer.