The 1200 error code indicates that the cartridge carrier has stalled. It could be due to the new black cartridge installed in the printer. Make sure you are using the correct version of black cartridge for your model and it's properly inserted in the cartridge carrier.
To remedy the problem, try to remove the black cartridge from the carrier > close the cover > unplug and re-plug the printer into the power source to reset it > when the printer turns on, re-insert the new black cartridge > check for any errors. If problem continues, try to insert a different known working black cartridge to determine if the new one is faulty.
For further troubleshooting, you may also refer to this article found in the Lexmark website: 1200
Error Message on a Lexmark X4250/X4270/F4270 All-In-One