I had the same problems unlocking an a217m, I was charged 2 times 5 credits for the mck code and it always gave an error when reading the nck code. but I deduct 10 credits. I wrote an email to z3x support yesterday but still no response.
that's the problem, I installed z3x on a new machine 2 weeks ago, and I don't see the folder where the logs are saved, there are all the other folders except that one. but I give you my box number to verify that what I say is true.
Thank you, but it will be for the next time that another team arrives, since the client took the phone.