The windows boot drive? Dont think thats possible anymore. If its completely new hardware.
Im not sure what the trigger is but if enough hardware has changed it wont boot.
I had to install windows fresh on a new hard drive when i bought a new pc last year.
If the partitioning is fine (GPT with EFI System Partition), it should boot up even if you move the disk to a completely new machine. You will need to re-activate Windows though after booting.
You may have had the ESP on a different drive than the one you moved to the new machine, perhaps?
Were you using BitLocker? You need to disable that before moving the drive.
Now that i think about it, i think it was an activation issue. I had a dodgey made legal copy of windows 10 when they offered the free upgrade to even those with illegal copies of windows, but when i moved it, i needed to activate and didn’t know the key.
But two replies offering different bits of advice to my comment shows that at least in part its true that this is not straightforward
