If you feel little or no resistance when turning it, then it's out of oil/there's air in the adjuster.
Wind it all the way out and take the pipe off the shock unit then fill it best you can with hydraulic jack oil, hold the pipe up, wind it in a bit to disperse as much air as possible and refit, wind it in a touch more to bleed it as much as you can when tightening the pipe back up.