I have the kit and am just now getting the Arduino / Ramps up and running. However, when I connect it to my computer it doesn’t show up as an available serial port in Repetier or the Arduino IDE. I have a Arduino UNO on hand and when I connect it I can see the USB modem1421 in both Repetier and the Arduino IDE. When I power up the mega/ramps I get two flashes on the green LED next to the 1K resistor on the ramps and there is a red led lit up on the mega and that it all.
EDIT: I removed the ramps board from the mega and just connected it via usb and it powers up but still doesn’t show up as a com port. It has the ON and L led’s lit up and that is all.