Windows 10 Product Key Stopped Working

[Surged]

So basically the title It just stopped working.
I have tried to use other keys my friends gave me but they won't work.
It started happening after I replaced my Motherboard.
I did get Windows 10 from the free upgrade with Windows 8.1.
So if any one could help me out that'd be great, I don't want to end up buying a 100$ copy of Windows 10.

Edit: Thanks for the answers Supahos and USAFRet. Helped a lot!

 

[Supahos]

The OEM version is tied to your motherboard, you can tell ms your board died and you had to replace it as a repair and they"might" give you a new key

 

[USAFRet]

So basically the title It just stopped working.
I have tried to use other keys my friends gave me but they won't work.
It started happening after I replaced my Motherboard.
I did get Windows 10 from the free upgrade with Windows 8.1.
So if any one could help me out that'd be great, I don't want to end up buying a 100$ copy of Windows 10.

It wasn't "random", it was due to a specific event that actually triggers this.
Changing the motherboard.

You have 2 options:
1. Call MS and see if they will allow that to be used with the new hardware
2. Buy a new OS for your new hardware.