Garageband recognizes midi keyboard but no sound

I have a brand new Casio CT-S200 keyboard, I hooked it up to my laptop with usb.

Opened GarageBand, checked the preferences, 1 MIDI input detected.

Created New Project, selecting Software Instrument.

When I try to play my keyboard, no sound or any activity in GarageBand.

I tried musical typing. It worked just fine.

My Casio works perfectly on it's own.

The usb cable is new.

I had it hooked my keyboard up last week and was able to use GarageBand with no problem.

Is there something I'm not doing. Something I forgot?

Is there something else that needs to be set up?

Any help would be appreciated!