Hi, I am Dave, I will help you with this.
On the 20th of September last year, Microsoft finally closed the loophole that allowed a Windows 8 product key to activate Windows 10 or 11 on new hardware, since they made that change, it is no longer possible to use the Windows 8 product key on new hardware.
The first problem you may have if you want to install Windows 8 on the new PC is to check if a full set of Windows 8 device drivers are available for the new PC on the manufacturers website, most likely they are not available, and if not, then you would experience many hardware errors on the PC if you install Windows 8.
Also, do you still have your Windows 8 disk, because Microsoft no longer provide an official Windows 8 ISO download.