What does this mean? printer message: change unable 51 see user guide

"Denise Greer use a small amount of warm water on a cotton swab until and clean the contacts on the cartridges, as well as on the printer as well. They are reasonable clean when no ink comes off on the swab.

If any cartridge is low, empty, leaking or bulging replace them. After cleaning turn off the printer, unplug it for a few minutes. Plug it back it and wait for the insert cartridges message then insert the cartridges and check to see if the problem is resolved. If it has not been resolved it could be a failed print head."