When you pull up and then down on the bottle opener do you hear air, (make sure it's not in the bottle, just pull up then push down to see if you hear or can feel air coming out) and is it an easy push and pull or is it a bit difficult?
Some Wine bottles do not work with the opener as the corks are not 100% snug so they will allow the air to escape and therefore it can not build up enough pressure to pop the cork.
When you are opening a bottle be sure to hold onto the bottle, not the clear piece.
One hand is towards the center of the bottle holding it, while the other is on the black shaft pumping air into the bottle.
If it feels like its a bit resistant to being pushed/pulled untwist the silver cap and add some olive oil/pam spray/vegetable oil (either one will work) to the top part of the shaft.
This acts like grease so that the pump can move freely.
Be sure not to pull up on it, meaning only pull on the shaft while pumping (make sure you are not pulling the spindle out of the cork) and do so gently when lifting up. You have to make sure the spindle is all the way through the cork, and that you do not move it up into the cork when lifting on the pump.
If you do not hear air there may be a piece of the cork stuck in the small rectangular opening on the spindle.
You can twist and remove the clear piece that covers the bottle so that you can clean out the spindle.
If this did not fix the issue you will need to file a claim. Under the warranty, the piece is replaced at no cost other than the shipping. Please locate the Warranty Section at the top of the page.