Are you at the correct bios?
Is the processor supported?
Have you contacted the motherboard manufacturer? Or, are we just assuming the board is good and it must be the processor that is bad?
Often, the board will require a bios update with an older processor to get it to the proper bios level for the new processor.
That is the path I would take with the board manufacturer.
At a minimum, you should be able to determine what bios came with the board.