Why do I have no sound on my Focus XD speaker when connected via the optical / coaxial digital input?

Check in the menu of the source device whether the optical digital or coaxial digital output emits a PCM stereo signal with maximum 24 bit / 96 KHz (Hub) or 24 bit / 192 KHz (Connect). Surround signals or up-sampling signals cannot be decoded by Focus XD.

Use another source with optical / coaxial digital output to test.