Roymondo:
You don’t say what type of tail lift it is.One strong possibility is that if the lorry is parked on a camber, the oil pick-up can be left high and dry as all the oil runs to the other end of the reservoir. Solution is to move the lorry to level ground, but even then you’ll often need to re-prime the pump. You do this by simply pressing the control(s) to raise the lift and hold it there until eventually the platform starts to move. It may take 30 seconds or more to respond.
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From the description by the OP it would be a hydraulic tail lift? So, Roymondo is (in my opinion) correct. Unless the unit has run out of hydraulic oil due to a leak in the system. (In which case, call your company. Somewhere at the rear of the vehicle should be a plastic reservoir/tank, about the size of a car battery. If it has no fluid in it, there is a leak which needs to be repaired). The “whirring” is the pump operating so not likely to be a fault with the electrons.