Drobo 5D3 won't boot

My Drobo 5D3 won’t start up at all. The yellow LED on the power switch is on, but when I click it, the lights all come on and the fan starts (exactly as if it’s going to boot) but after anything between 0.5s and 5s all the lights go out and it stops.

It’s doing this without any drives in. I’ve tried replacing the external power supply from another Drobo which works properly, and get exactly the same problem. So it’s not the power supply.

Any thoughts before I source a replacement?

Martin

Will it boot without any hard disks?