I formatted my PC without removing my license. Now, I can’t activate it again on the same PC. I tried the single-user method and that didn’t work. I tried adding the license key to my cloud account and it says I have to remove it from that PC first and that’s not possible! I upgrade my PC’s cpu and motherboard and now Windows’ license is being retarded too. This is maddening!
I think Windows checks the network-card MAC address, so you will have to call MS up and have them reactivate the license (I had to do that once). On another machine I just replaced the hardrive (to a SSD), that deactivated Win10, but it got activated again when I pressed “Troubleshoot activation” (or some such link in the system settings). A new motherboard is likely to have a device with a Windows-dependent MAC address which now have changed, so a phone call to MS is probably needed.