Silent Killer perk

Hi, kinda new to the game
I've been using this perk for the last 10 levels and I just noticed it never worked

Is vanish cd supposed to reset after each kill ? Because i've been trying to make it work now and i cannot make it work, is there something I dont understand ?

I vanish > kill a mob > jump again but it doesnt proc next vanish ?
I always need to wait 5 seconds for vanish to work again, whatever I do

 

resolved !