I've noticed that they work better at some lakes than others. They work awesome at Indian lake. The 2 smallest sizes work best and you can really snap them up and down.
I've learned that up on the Northeast ohio lakes for Walleyes that the 1/2 ounce works well with a very subtle jerk and let them sit for a while before jigging them again. The walleys like to hit them when they are sitting still.
On Buckeye lake the jigging rappala works the better than the Vibe for some reason.
Keep trying them and i am sure they will produce for you