Servo Calibration Rover

Hi,

Building the Mars Rover I may have encountered a Problem. At a certain point it says, connect Servo to the Rover (Servo 2) for Zeroing. When connecting properly and turning the Rover on, the Rover says something and lights are flashing. So far so good.

But the connected Servo ist only constantly „humming“, not very loud but the gears are not turning at all. Is this correct behaviour?

BR
Jan