If the clock is set to ADAT and it shows unlocked, assuming you have checked for the bug I mentioned earlier, you either have a bad source, or a bad cable or a bad H8000.
Double check your connections – this is the most likely issue. Make sure that you can see red at the end of the ADAT cable.
You can do a simple check of the H8000 by setting it to 48k internal clock and connecting the "ADAT in" to the "ADAT out" – it should then show "ADAT locked". If not, contact email@example.com