I had the same problem. You may prefer to call Humax support (and I suggest yoiu do) but what finally solved it for me was powering down, removeing the lid, disconnecting the hard disk power and sata leads and powering up.
This worked fine (initial meesage no HD detected).
Powered down reconnected – Powered up – all O.K. – very strange.
Note: After power off the red Led seems to fade about the time the power supply capacitors would have discharged (wonder if this is by design?)