No sound

Is DHT-S516H’s volume turned up? (Don’t laugh; we do this one ourselves all the time.)

Is DHT-S516H muted (if so, the front LED is slowly blinking.).

Is the audio source a volume-controlled television or cable/satellite box output? If so, you must turn up the volume of the television or cable/satellite box to send adequate signal-level to DHT-S516H. (For this reason it is best to choose fixed-level outputs where possible; some televisions have separate physical outputs, other employ on-screen menu settings to manage this.)

Check connections: remember that DHT-S516H auto-prioritizes multiple incoming signals, selecting HDMI, optical-digital, coaxial-digital, and analog-mini plug, in that order. Confirm that the television is routing audio to the appropriate output; there may be TV-menu settings to manage this.