If you got a new computer system recently then it probably is using UEFI bios and it didn’t come with Windows installation media or a product license activation key. What gives?
Manufacturers are now embedding the activation key in the UEFI BIOS. You can retrieve the key by running this command from within a Windows powershell session:
wmic path softwarelicensingservice get oa3xoriginalproductkey
I moved my hard drive to a new Dell OEM PC (new motherboard/chassis/etc.) recently and had to activate windows 10 again once I was up and running. The activation kept failing. I found this out and went to the activation window, hit the “Change key” option and then ran the above command and pulled the key out of UEFI Bios on the new system and it worked without a problem. I had to change the key in my Windows 10 install to match the key stored in the UEFI Bios on the system. Thankfully my Windows 10 install from my old system was the “Pro” SKU and that is what the Dell workstation originally came pre-loaded with.