My guess is Updater was able to erase faulty firmware, after that you disconnected USB, so no new firmware loading and the result is System software missing.
You must keep and holding on screen until Upater finishes.
If you get IOU_Utilities error it's because USB connection is not good anymore and preboot fails.
As said reasons can be: bad cable, bad USB port connection, USB hub use, not supported USB v3, wrongly followed preboot and flashing procedure.
Pc doesn't see gps because cure didn't load.
I need to unplug/re-insert the USB or the process never gets to the "Erasing" step. It then continues to write something to the GPS - at least according to the PC status messages. I've tried at least 3 different cables on two different laptops. If I don't pull the USB cable, I always get the IOU error.
I think they were USB3 ports - directly on the laptop - no hub. I'll try next on a USB2 port somewhere...