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?
I’ve done that multiple times without issue.
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?