This happens either due to interruption of the USB connection or the Internet connection.
It’s a tricky issue but it can be fixed very easily.
We advise you to connect the device to another computer and update the firmware from there.
Before that try the following:
- Restart Computer
- Reconnect device
- Power cycle device
Worst case scenario: initiate Golden Boot sequence but only after you have tried multiple computers. Have in mind that we do not advise this because Golden Boot could leave the device completely unresponsive and make it harder to connect and update.