This issue can happen if the cartridges are inserted into the incorrect slot. Please verify that the cartridges are seated in the order that they appear in the image below:
Were you able to test the machine with the new cartridges?
Since the ink is in the correct order and the ink is still backflowing, there may be a issue with the print head. I would normally advise that you get the printer serviced but the IP4000 has been retired and service/parts are no longer available.
You would qualify for the Canon Upgrade Program.This is for out of warranty units which have been diagnosed to require service or are incompatible with a new or upgraded system. This program allows you the opportunity to purchase a replacement product discounted from the list price. Free ground shipping is included with your purchase.
If you would like to take advantage of this offer, please call our Sales Department at (866) 443-8002 Mon-Sat, 9 AM to 9pm EST.
Let them know you have been working with technical support and that the Canon Upgrade Program was offered.
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12/05/2023: New firmware updates are available.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.