Hello, Superman:
Notation products are very good at recognizing midi devices, but there have been some issues in the past with cheaper midi interfaces not being reliable. To be clear, that's usually a problem with the device, not Notation products.
Does the Clavinova appear in the Midi Device Quick Setup or Midi Device Configuration lists? If so, make sure you've selected it as an input device and for playback.
There's a great piece of software called Midi-Ox (don't ask me why) that monitors midi activity and lets you see what your midi device is doing. It's here :
http://www.midiox.com/
Try downloading and installing that. Use the "blue circle with yellow dots on it" icon to view and select your midi devices. If it's properly installed and working, you should be able to play notes on the keyboard and see the result in Midi-Ox's monitor boxes. If it's working in Midi-Ox, it
should be working in Composer.
Let us know what happens, please.
David