Sylenth 1 velocity issue in Cubase

[rayoliver87]

Hi guys. I'm having a bit of trouble in Cubase 6 with Sylenth1. When i open the key editor and try to alter the velocity of certain notes, nothing happens to the sound. It writes it in, but when i play it, the notes are all still the same volume. is there something else i need to activate for it to work?
thanks