Black ink cartridge not working on Canon Pixma TR4720

I'm not sure if this question belongs on this site, this post says it does. I posted it on the Canon community but nobody answered it. The printer was just working fine when I was printing some photos in black and white. Then, the photos started to get light, so I assumed the cartridge was clogged. So, I ran some cleaning cycles, well aware that it probably used up a lot of ink. It still doesn't work. I read that ammonia helps unclog cartridges, so I soaked the bottom of it. Five hours later and still no luck. I put some ink into an old cartridge but that won't print at all either. I think it

Question by John Doe on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.