Gargh.
So I didn't update the firmware on my DN2820FYKH, maybe that's to blame, maybe I fat fingered twice.
But I managed to set the user and master password for the SSD to be something that it doesn't recognise. I'm confused by this because I used the same password for the BIOS too (yes, I know, that's bad). Yet the BIOS ones both worked fine.
On actually reading the manual, I noticed that it says passwords should not be longer than 8 chars.... Oops. So I tried typing the 8 char truncated version and no, it still doesn't like it.
Any ideas? My understanding is these passwords are stored in the firmware of the SSD.