Speaking of Win 10 Pro. This morning I received a message the my OS is not activated. What happened was I had a dual boot with Win 8 and I deleted that partition so I could just have 10. 10 was activated because of 8, now that its deleted 10 doesn't see an activation. I tried to use the 8 pro key that doesn't work. 2 things I can do, install 8 again then upgrade to 10 or buy a key for 10. Either way I have to start all over again.
When I went to the Microsoft to buy a key it told me I have to buy a Home key. As Jafo said "being told your Pro licence isn't real/legal...kindly Install 'Home'".
Here is the global volume license key for Windows 10 Pro.
This is a legal publicly available key. It's available from this MS site:
The trick is that you will need a KMS server or simulator to activate.
Windows 10 doesn't just usually lose a key.