It could be any of the things already mentioned, and without knowing your skill level it's hard to be specific as to the cause. My first instinct would be to check your pads for good sealing and check the keywork for correct adjustment. If you can do this yourself then do whatever you can while avoiding anything or any action that might void the warranty. If not, then first, get somebody who can play competently to try the instrument. If it works for them then the problem is mostly with you. If it doesn't, then if the instrument still under warranty then I think you need to discuss this with the supplier.