you more than likely lost the prime on your machine,
what you need to do is get a syringe, take the needle off
remove the maintenance cover where the printer parks the head, then remove the metal cover over the pump ( three screws at the bottom through holes in front of plate) pull off the lines to the pump from the capping stations there are two lines that go to a Y move the lines one at a time at the Y put syringe on the line draw back slowly to re prime the heads, if you cannot get a prime
move the print heads over in the cleaning menu, and fill the capping stations with cleaning fluid, re-park the heads and pull on the syringe this should re-prime the heads of course you only need to do the one that is out.. the black and cyan are on the same head..
//chopper