With the printer turned on, unplug the power cord from the rear of the printer.
You must disconnect the power cord before reaching inside the printer.
Lift the carriage latch, slightly lift the printhead, lower the printhead back into the carriage, wiggle the printhead left and right, and then lower the carriage latch to lock the printhead into place.
Close the ink cartridge access door.
Reconnect the power cord to the rear of the printer.
Sometimes error messages persist after inserting the printhead. If the error message persists, repeat the steps to reseat the printhead up to three times.