Not sure on a S250.
On my manual controlled 742B the lift peddle needed to be pushed down all the way with the toe until the detent locked. Almost had to slam it down to get it to catch.
On my A300 with joysticks, you lower the arms all the way press the ”float” button (has a bucket with arms symbol on it) and then while holding the float button in, bump the joystick all the way forward and release.