Two comments. First, you have to have the nozzle up to temperature before Marlin will attempt to move the extruder motor. It will typically issue a 'Cold extrusion attempted.' message if the nozzle is not hot enough.
You may need to turn up the current going to the extruder stepper motor. There will be a little potentiometer on the step-stick on the RAMPS board. Be very gentle and careful. ideally you should use a non-metal screw driver to turn it. It is possible you don't have enough current going to the stepper motor.
You may need to turn up the current going to the extruder stepper motor. There will be a little potentiometer on the step-stick on the RAMPS board. Be very gentle and careful. ideally you should use a non-metal screw driver to turn it. It is possible you don't have enough current going to the stepper motor.