If you have tried several cleaning and the PGBK is still blank, it looks like the print head might be clogged or damaged. In this situation you can try reseating the print head using the steps ink the link provided HERE. If that does not work, you can try another PGBK ink tank to see if that resolves the issue.
If reseating the print head does not work or the new ink tank, it looks like the printer would need service. The printer has a 1 year warranty and you can click the link HERE to create a Canon account to see what service options you have.
Outside of the 1 year warranty, you can contact our sales department at 1-800-652-2666 to use our Upgrade Program. The Upgrade program will give you a discount and free shipping on a replacement printer.