Had a cartridge error message. Changed the 4 cartridges with new cartridges. Same error message. Followed all the steps in the HP Support and tool box. Nothing worked. Took out all the cartridges, looked into the cartridge holder and saw a silver lever to the right of the black cartridge holder with the word 'LIFT" on it. (Put on some gloves because the next step you may get some ink on your fingers!) LIfted the lever and the cartridge holder easily pulls out. I then reinserted the cartridge holder carefully because there are a lot of pins on the back, and inserted the 4 used cartridges and the error message no longer appears. I was able to resume printing.
Don't know why HP doesn't put this on its support web site.
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