The Tablo 4Gs (and perhaps others) have been misbehaving recently. Don’t know when this is going to be fixed (properly) but I wouldn’t blame the firmware update just yet - I think the problem is on their end, not ours.
I checked power supply and it was still providing 12V. But when I test the USB port on Tablo device there is no power. So I ordered a new 12V power supply. Verified again that new power supply is working but that changed nothing.