I recently purchased a RAMPS 1.6+ and it connects to my Arduino Mega 2560 just fine. I am able to use Pronterface to heat the extruder and the hotbed but the motors refuse to work. I have the jumpers configured the way they should and have the "Reset" and "Sleep" pins soldered (because I'm using an A4988). But the motors will not move.
I was using a RAMPS 1.4 and the drivers worked fine with that board. I do not know how to fix this problem. I did recently upgrade to Marlin 2.0 so perhaps there is a configuration issue? I have the steppers defined in the firmware.