I bought a Windows Ten Pro key and it doesn't work...

CVRIV said:

I had no idea. I just thought it was a Win 10 Pro. Thats it. Even though I got a bangin deal on the keys... It's still not fair to me. I bought the keys because I wanted to be legit about it. I could of easily found ways around that. So even though I paid money, Im still not legit. Very disappointing.

Yes, they should be reported. Like others said, if the price seems to good to be true, it probably is. As you have discovered, people will see MSDN keys, OEM keys, etc.

Keys can be sold again if they're activated from a device I think.

If it is a Retail Key, yes then it can be resold after the key has been deactivated from the previous device that used it. The next user using the key to activate their instance of Windows, might have to activate it over the phone though.

Check to see if the key is valid for any windows version:
ShowKeyPlus

Then you can use it to activate windows 10 via this route:
Clean Install Windows 10 Directly without having to Upgrade First