Razer Phone 2 Unlock help

So I have a Razer Phone 2 that I'm trying to pass on to my brother. It is carrier-locked to ATT but ATT has approved the unlock and sent me the unlock code. My issue is the phone won't accept the unlock code. When the code is inputted it says "sim network unlock request unsuccessful." Anyone know of a trick to get these things to unlock? ATT isn't much help as they said they have approved the unlock and sent me the code in their database to unlock it and if the phone isn't accepting the code it's a Razer issue.