B2 means “Legacy Option ROM Initialization”: https://www.supermicro.com/manuals/other/AMI_BIOS_POST_Codes_for_Grantley_Motherboards.pdf. The customer's issue was fixed by doing a BIOS recovery with the latest BIOS : https://www.supermicro.com/manuals/other/UEFI_BIOS_Recovery.pdf