Bricked Sidekiq Z2

I cannot now access my Sidekiq Z2.  The USB gadget and storage storage are now not appearing in my Ubuntu host.  On accessing prior to bricked, after I ejected the USB storage device from Ubuntu it always automatically re-appeared after a few seconds.

I had removed the USB cable from the Sidekiq as soon as Ubuntu reported it safe but on re-boot of the Sidekiq it is now bricked.

Is there another way to access the device Linux and factory reset?