Weird, looks like the user who sold you the key isn't MSDN or genuine as that's what it says in the error. It normally says "Acitvation Success" or something along those lines. He sold you an invalid MSDN key.
I think I may have experienced the same thing you did yesterday. I formatted my hard drive and installed Windows 10 (alongside Elementary OS). I couldn't activate it at all and always encountered an error; luckily I had the latest Windows 10 iso that was pre-activated, so I just installed that and haven't had a problem since.
If you need the iso, add me on skype.