No sound in Garage Band?

I just got MacBook Pro. Garage Band seems to be picking up guitar as the tuner is working. The equilizer in the track is showing nothing. I changed to audio input on System Preference and Garage Band Preference. Checked on amp for audio input. All volumes up. Any help would be greatly appreciated. Really looking forward to using this program. The same thing happened when I did it with my wife's new IMAC.