Communication ok but motor does not move

[AlwaysY]

Hello

I bought " Stepper Motor Nema 17 Bipolar 40mm 64oz.in(45Ncm) 2A 4 Lead 3D Printer Hobby CNC " and the " Makerbase MKS SERVO42A NEMA17 Closed Loop Stepper Motor Driver" on Amazon, assembled it according to the youtube manual on github and connected it via USB to a PC as shown attached. Upon plugging in, the red diode turns on for a couple of seconds, and then turns off. I use RealTerm Serial communication 2.0.0.70 to talk to the driver. Calibration commands seem to work. However, none of the move commands (e.g. "step 1", nor "step 1 16" or "move 300") work, the motor does not move at all, but the commands are accepted as valid. Can anyone suggest a solution?

Help is much appreciated, thanks!

AlwaysY