good luck with that.
For over a month I tried to contact MS support, opening at least 4 tickets. All of them were close after a while, saying the problem was solved. Ridicolous, to say the least.
I just solved myself using the same unofficial tool used by some of their own staff to unlock this issue and finally solve it. I bought a full price, retail license but after this experience I'll never do it again, IF I will ever buy some other license will be through some website selling cheap keys.