New RAMPS 1.6 not working
Pins are sometimes different between the two shields.  I ran into one a while back... Go over the pin specs for the 1.6 one at a time.
Correction: pins are SUPPOSED to be the same.  I've however experienced them not being the same.  I don't know if my 1.3s were the oddballs or if the 1.6 was.