If it has voltage and does not engage, it may need adjusting. There are three nuts that adjust the clearance of the clutch when not engaged, if it is too much the magnet won't draw it in. Set the clearance to 0.018", there is three inspection slots to do this. These clutches are reliable as can be, but if that clearance is out of spec it won't engage. It is one of the most common problems with those units.
Wayne