I had the same issue. Apparently the fewer harddisks you added to your system (I got 3 x WD Red 8 TB) the longer the initialisation takes and you shouldn't touch the Drobo Dashboard during the process. So your best bet is to simply leave it alone for a day or two and it will do its thing. Also, the first time you switch it on, the harddisks should not be inserted yet. Then it will update the firmware. At least that's what did the trick for me last week.