The fixed bin cleared the MAC address. Fix: You cannot change it in Windows permanently. You must use an EFI shell or a DOS tool called EEUPDATE.exe (for Intel NICs). Alternatively, note down the MAC from a sticker on the motherboard and manually enter it via Device Manager > NIC > Advanced > Network Address.
A has been:
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If the system is not booting (POST failure), you can attempt a recovery before hardware flashing: [Help Request] HP Pro 3500 MT BIOS Recovery The fixed bin cleared the MAC address