Any of following factors can be considered. Please confirm in order from the top.
Off the setting of Mute/Solo of track editor.
In case master fader is downed at the bottom on mixer screen, bring it up to the 0dB position.
Reset setting of Mute/Solo button on mixer screen.
If you select the Voicebank which is not authenticated, no sound comes out. Authentication of Voice can be confirmed from VOCALOID Authorizer.
Please check if appropriate device is setting from audio device of preference.
If you apply the song data to your Voicebank from "VPR file" or "VSQX file" with a different language, you may not hear any sound even though lyrics are displayed. Please re-input the lyrics for them to sing.