windows ten makes a note of the unique code that is in the MB BIOS and embeds it into the windows OS, this is what stops the system booting when you change the MB.
it has done this to try and get you to buy a new copy of windows,
there is a way to use your existing copy of windows, which can be found on the MS website, My son recently used his old win 10 codes on a new system that he just had built, I cannot give you anymore info on what he did ATM as my son is not about.
When I know more I will let you know what he did