Can't activate Windows 10 Pro with license linked to Microsoft account or product key

The Windows 10 serial is associated with the old hardware. It is registered with your Microsoft account, but that is only for the purpose of easily activating the old hardware.

Microsoft takes into account too many parameters of your old hardware, you cannot trick it into activating the new hardware with a serial that was already used.

The old activation key was apparently an OEM license that came with the old hardware, maybe it was even burnt into the BIOS. It cannot have been a Retail version, because Retail keys are transferable.

So, sorry, you need to buy a Windows 10 serial for your new computer.