Hi friends, I think you still remember, that you could make a Retail "genuine" copy out of a KMS activated machine with one of these WMC Retail keys. Today I changed my motherboard after upgrading that said activation to Windows 10 Pro. Of course the OS was not activated anymore. So I decided to contact the support via the support app and they gave me a retail Windows 10 Key and activated my machine again.
You got lucky then !! To me they told bad luck go install windows 8.1 again andd upgrade or buy a key after changing my motherboard