Volumes faders move down when play midi Keyboard????

I’m new to cubase, I’m learning. I have a midi controller which I’ m connecting to my cubase. Everything works but when I try to play or to record all my channels fades their volume to 0 in the MixConsole and I can’t hear nothing. Is anybody there who may tell the tricks. What can I do to hear my midi tracks when I’m recording or playing my midi controller!