BTW these new machines, doesn't reboot nicely. Sometimes (not every time) when rebooted, the miner is still busy with the previous session, occupying the usb drivers. When the PI is rebooted, It can't find the usb devices, so this is why it wasn't hashing after the firmware update (which is followed by an automatic reboot).
But once it's running, it will keep running. Just remember to do a power cycle after reboot (and firmware update)