There is no boat wake at the cable, so you generate the pop yourself: in the final third of the approach pull the handle toward your hip, load the edge hard, then pop off the kicker.
At the boat part of your take-off comes free: the wake acts as a ramp. At the cable that wave does not exist, which is why line loading there is not a finishing touch but the precondition for any height at all. You build tension in the line by deliberately pulling the handle a few centimetres toward your leading hip over the final metres while loading the edge — at the take-off point that tension releases as pop. The most common mistake is not a lack of force but late timing: start loading at the kicker's lip and you barely leave the water, however steep the ramp is. What tends to get missed: line loading does not cover the landing. Knee load in wakeboarding comes mainly from axial compression on touchdown — the higher the jump, the more the active cushioning through knees and hips matters.