I recently changed 3 ink cartridges on my CanoniPF5100. The red lights were blinking to indicate low ink. Two were replaced with new carts and worked properly, but the third failed to recognize the PC cart. The cart light never came on. I cleaned the internal contact with alcohol and electrical contact spray...no improvement. I also swapped in another new PC cart with the same result. All cartridge lights are lighted except PC. Any ideas?