A device that fails to start after an interrupted upgrade can often be recovered. Repeatedly power-cycling it is the wrong instinct.

1. Establish the symptom: watch the LED for a breathing pattern and see whether the search tool can still discover the unit. If it is discoverable, a second upgrade usually restores it.
2. Check the file: confirm the firmware matches the model and hardware revision exactly, that the extracted file is intact, and that the package is not sitting in a non-ASCII path or on a network share.
3. Upgrade over cable: always use a wired connection and a stable power supply. Losing power or network mid-upgrade is the number one cause of a bricked device. Do not touch the device while it writes.
4. Vendor recovery tool: some manufacturers supply a low-level recovery utility that rewrites firmware over serial or TFTP. Obtain it from vendor support.
5. Deciding to return it: if none of the above works, return the unit and describe exactly what happened, so the fault can be traced to corrupted bootloader or a storage chip.

Operationally, validate an upgrade on one unit before pushing to a fleet, and record the current version and configuration so you can roll back.