Digital studio · declared evidence
ADAT locked, but no sound?
Use clock lock, source and receiver meters, DAW input and a controlled cable test to isolate digital audio silence, clicks or missing channels.
Your observations
Lock and audio are different observations
A locked indicator shows that a receiver recognizes a timing reference; it does not show that the intended microphone is routed to the optical output or that the DAW selected the correct input. Follow one channel through source meter, receiver digital meter and DAW input meter before changing more than one setting.
Example: lock yes, source meter yes, receiver meter yes, DAW meter no points to the receiver-to-DAW mapping as the next layer. Lock yes and source meter no instead puts the source/input/routing before the cable. A reported rate mismatch or conflicting observation gets attention before these downstream conclusions.
Use a cable swap as a control, not a verdict
If a correctly specified known-good cable changes the outcome, keep every other condition fixed and repeat once. The original connector seating or route may also have changed. A no-change result is not universal cable certification. With clicks, watch lock over time rather than trust one snapshot; with channels missing after a rate change, compare the S/MUX port map.
Do not reset equipment blindly, inspect optical emitters, record/upload audio or change electrical wiring to follow this worksheet. Sources: Focusrite ADAT troubleshooting and standalone digital-output routing.