Z axis calibration 2021 M2

Hi Everyone! I’m super new and just set up my m2 today. going through the calibration settings i got to the z axis but couldn’t set a define zero.
the button just doesn’t appear to do so?
i continued though the other calibrations and got to the precision section where it nearly broke the whole sled trying to push its way all the way through it. i had to unplug the usb to stop it. i tried again and it did the same thing.

any suggestions?
thanks