Flashing firmware manually is a high-risk procedure. You should never unplug the USB cable or the power cord during the process, as this can permanently damage the main PCB (circuit board) of the printer.
Reinstall Brother ControlCenter via the Brother support website for your printer model.
: While originally designed for older Windows environments (like Windows XP 32-bit), it is often run in virtual machines to recover older hardware. Typical Recovery Workflow Enter Maintenance Mode