This usually means you are trying to flash a BIOS meant for a different MSN version. Double-check your serial number.
Medion typically does not list BIOS updates in a public "general" list. You must enter your MSN on the Medion Drivers & Updates page to see available downloads. medion b460h6em bios update fix
If you followed the SPI flashing instructions correctly, you have a 95% chance of revival. For the remaining 5%, accept that OEM motherboards are disposable. Sell the CPU and RAM, buy a retail B560 board, and never deal with MEDION's locked firmware again. This usually means you are trying to flash