Originally Posted by zquesti0nmark7
Does anyone on earth have a clue whats going wrong? I sat on the phone with AT&T, HTC, and T-Mobile for hours and no one has a clue why I'm not being asked for my unlock code upon inserting the sim card, please I cant be the only person who has had this issue, i have now tried many hard reboots, unlocked boot loader, even flashed maximus 7 HD to try and reset the counter and still no luck.
I also recently bought an AT&T HTC One from Craiglist. When I inserted a T-Mobile SIM card it prompted me to enter the unlock code, which I entered then the phone rebooted and it no longer asked me for the unlock code.
BUT, i was not able to get a signal and got the MM #6 error.
The error apparently can be from the phone being black listed. in my case the phone is not blacklisted.
The other reason, it seems, since the phone was bought from AT&T with subsidies, AT&T will not allow the phone to be used on t-mobile.
Had the previous owner requested the unlock code before selling it then it would have been unlocked.
For now, I am using it with aio for $40/month which is pretty good.