Check to make sure that the wires are correct. If you hit the home-all-axis function, you should get all 3 axis hitting and endtop. If it is set in the wrong (for example, X motor wiring is reversed, AND you put the endstop on the wrong side) then the endstop will be hit, but the program didnt know what to do. Endstop being hit automatically prevents that axis from being used. To remedy, turn off motors, and move the axis by hand out of the way. Set X=0 manually if you have to for now.