Get stronger first
Jumping is producing a lot of force, fast. If you can't produce much force slowly, you can't produce it quickly either. A solid squat or trap bar deadlift is the base everything else sits on.
Jump less, but better
Plyometrics work when every rep is fast and fresh. Box jumps, bounds and depth jumps in small sets, with full rest between. The moment reps get slow or sloppy, stop.
Volume isn't the point. Intent is.
Use your arms
A big, fast arm swing adds real height. Practise it. In GRID we measure a countermovement jump, so the dip-and-drive matters too: quick down, violent up.
Where's your jump now?
Vertical jump and the med ball chest pass make up your GRID power score. Get your number in about three minutes.
Rest like you mean it
Power training isn't conditioning. Take the time between sets that lets the next rep be your best one.
Give it a block
Two focused sessions a week for eight weeks, then retest. That's long enough to see a real change, and short enough to stay sharp.