Problem with reproducing audio

Hello, I have a problem with my audio plugin. I am trying to program a simple drum pad sampler, and everything works fine when in Project Settings the option Plugin is a synth is turned off, but then my host recognize it as an effect and not as an instrument. When I turn on option Plugin is a synth, host recognize it as instrument but plugin wont reproduce any audio, it behaves like it is not getting midi messages. I use Ableton as a host, and in my processor class I use keyboardState object for processing midi messages and then process audio buffer. Why is this happening? Am I missing some settings setting right?