FrostFang support item bug

On mid lane turret with my minions already pushed to the enemy turret I wanted to attack the turret to use my 3 frost fang stacks that I had up. As ziliean I attacked at least 6 times and not one of them used a charged to give me 15 gold. I have seen it work countless of times and I have seen it not work. This is without me killing anything, I just walked up to attack turret and nothing happened.