Windows 10: Trouble activating a legitimate product key for Windows 10 on a new build pc that had...

My son and his friends built a PC yesterday, and installed Windows 10 Pro using a friend's USB. We decided it would be best to have our own legitimate Windows 10, so we purchased Windows 10 Home from the Microsoft store and downloaded it. The activation key is not accepted. The computer says the windows 10 pro version is still active. We've tried selecting "change product key" and that doesn't work. Not sure what to do. Any help a beginner can understand? Thanks

:)

 

Invalid Product Key on legitimate windows 10 copy?

So, I recently bought a CyberPower PC from Best Buy with Windows 10
Pre-Installed on it. Everything seemed fine until a few hours after the computer was on, when the infamous Activate Windows watermark showed up. When I checked the Activation menu, there was a listed product key that I assume had come with the PC, but
Windows said that it was not a valid key, and that I should buy a genuine copy of Windows. (Error Code: 0xC004003)

There is no other product key within the computer's packaging, and trying to find this existing key through CMD has rendered no results. I have legitimately found no similar problems to this on nearly a dozen threads. I really don't want to spend $50 on
Windows 10, something I already paid for, or start having to make a habit of manually turning off the watermark in the registry editor and restarting my computer every few hours so I don't have to deal with it
because of something that isn't my fault.

The only conceivable reasons that I could seem to find that would make Windows not like this Product Key is that either the people at Best Buy upgraded the PC from Windows 7 (Which is strangely the listed backup OS on this PC) incorrectly and installed some
hardware drivers in the wrong order or something, or "The Windows 10 Activation Servers are Running Slowly, and My Version Will Activate in a Matter of Days," which is looking less and less likely as nearly a week will have passed at the conception of this
thread.

Sorry for the massive wall of text, but I wanted to give all the info I could. If anyone has any other solutions, I'd appreciate it.

 

Need help with transferring Windows 10 to new PC

*Nevermind I figured it out. I just bought a license key for $29.00. Thx though.
So my friend asked me to build him a new computer for work. The last one I built him was during the windows 7-10 upgrade grace period. I used to load windows 7, use windows loader to put in a product key, activate it, then upgrade to windows 10. Now that the grace period is over, and I'm working with new hardware, I was wondering if it is possible to install windows 10 from an already functioning computer that operated on a sata SSD to a new computer with an m.2 nvme SSD, using just the product key from the current windows 10 off of his computer. I use a program that grabs the product key called ProduKey.
Should I do a fresh install of windows 10 using his key after deactivating it from his current PC , instead of cloning drives correct? It would be nice not to have to pay microsoft $200 for windows 10 if he already has it and plans on not using his old pc anymore.

 

Windows 10 Activation (Insider)

Like Pill Monster said no more Windows 10 keys for Insiders. It was on Microsoft Blog they said that all that stuff is tied to one machine. You can upgrade anytime but never make a clean install. Those people who upgraded from 7 or 8.1 to 10 can do a clean install of RTM and post-RTM builds. A friend of mine upgraded from RTM to 10533 or whatever the latest post-RTM build is (and it activated just fine).

After all MS isn't stupid to give Windows 10 for free.