Have you downloaded and installed the latest driver for your device and selected it in Cubase?
http://usa.yamaha.com/products/music-production/interfaces/audiogram/audiogram3/
Are your speakers/headphones connected to the Auidiogram?
Can you hear the input signal out of the Audiogram’s outputs even when Cubase is not running?
Is the option for Direct Monitoring available in Cubase Device Setup?
Your system specs (Mac/PC, etc.) might be helpful, too. 