Canon MG6400 SERIES Online Manual page 157

(2) Press on the top of the ink tank until the ink tank snaps firmly into place.
Make sure that the ink lamp lights up red.
Important
You cannot print if the ink tank is installed in the wrong position. Be sure to install
the ink tank in the correct position according to the label on the print head holder.
You cannot print unless all the ink tanks are installed. Be sure to install all the ink
tanks.
7. Close the operation panel gently.
Caution
When closing the operation panel, be careful not to get your fingers caught.
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