Imported Midi Files do not Play Drums

I am new to Cubase AI, but have experience with other recording software. Today I just imported a dozen or so complete midi files. Everything plays except the drums in each file. My first guess was that the drum tracks were muted, but those buttons had no effect on the drum tracks playing in General Midi. I think I need help with drum mapping basics, Can you help me just get started with this?

Thank you.