The Canon MG3640 cannot physically see inside the cartridges to find out how much ink is actually left. Instead, the copper contacts on the outside of the cartridges contain this information. The ink levels start at full. Every time a page is printed or a head cleaning routine run, the printer writes this information to the cartridge. Eventually, the cartridge will state that it is empty. However this may not be the case, and it may be possible to use the remaining ink in the cartridge.
If you have refilled your cartridge, or have purchased a remanufactured one, the copper contacts will already hold the information that the cartridge is empty. Clearly they are not, but it is not currently possible to reset the ink level information on the copper contacts of the cartridge.
Instead, you simply need to override the empty error message that is being displayed by holding down the “stop / reset” button on the printer for around five seconds. The printer should continue printing, and use any of the remaining ink in the cartridge.
If the printer thinks that both cartridges are empty, you will receive a second error message, and you will need to hold the button for another five seconds.
If the circuitry on the cartridges is actually damaged, unfortunately, this process will not work.
Youtube Video: Override the empty cartridge message.
Youtube Video: Change Ink Cartridge