Question MiniDSP 2x4HD won't turn on after flashing wrong firmware --- can it be fixed ?

If you can't flash the firmware again, by using correct firmware, then your device is toast.

You could contact device manufacturer and ask them for a repair, but if they are not able or willing to repair it, you need to dish out another 260 bucks (price on Amazon) to buy a new one.

You can call it life's tax.