I had audio problems with my headset awhile back and called MS support and they walked me through a fix. I know your issue is with a mic and mine was more sound related but this might fix your nephew's problem too.
Here's the chat I had with MS support. Follow the steps starting with the line of RED text.
Andy: Hello, thank you for contacting Xbox Customer Support. My name is Andy. How can I help you today?
you: HI Andy. I'm having a problem with my new xbox one controller.
Andy: Hi Leemz! I understand that you have an issue on your controller. NO worries I will do my best to help you.
you: ok thanks. yesterday afternoon it was working perfectly fine. however, when i went to use it again after dinner a few hours later, i noticed that i wasn't getting any audio from the stereo headset.
Andy: Thank you for that information, may I know what steps have you done before contacting us?
you: i plugged the headset into an ipod and the headset worked fine. so i assumed the issue was the adapter. i went to the store where i bought the headset and they swapped out the adapter but when i got home, the headset still didn't work. so i then assumed the problem was the controller. so i bought a new controller and the headset is now working so i have to assume that the gamepad is the problem. everything else works with the gamepad except no audio.
Andy: Thank you for that information.
you: i'm getting no audio from the headset (xbox headset by the way) and the chat set.
Andy: For us to resolve this, we might need to do some steps that will possibly resolve this, if the steps did not work, we need to request a replacement okay?
Andy: I will provide the steps now. Are you ready?
you: ok, let's give it a shot.
Andy: Alright!
Andy: Please go to Settings>> Disc & Blu-ray >>Persistent Storage >> Clear Persistent Storage. Please do this step for 3 times.
Andy: Please let me know once you'jre done.
Andy: *you're
you: ok gimme a sec. i'm sharing a monitor with my pc and xbox so i have to switch back and forth.
Andy: Alright!
you: i'm using new controller now. do i need to use the "broken" one?
Andy: Yes please use it now.
you: ok, i gotta swap out the battery pack.
Andy: Alright!
you: ok, storage cleared three times.
Andy: After you have done clearing Persistent Storage, please go to Settings >> Network >> Advanced Settings >> Alternate MAC>> Clear Alternate MAC >>Restart
you: ok.
Andy: Please let me know once you're done.
you: ok, restarted and back up.
Andy: Alright! Please sign in and try to join a party.
Andy: Please let me know the result.
you: ok, i'm stupid. how do i join a party. haven't tried on the xbo yet.
you: do i need the chat set plugged in?
Andy: Oh, yes please.
you: can it be the headphones instead?
Andy: There is a possibility but we still need to check okay?
you: ok, how do i join a party?
Andy: Join a party that your friends are already in
Andy: 1.To return to the Home screen, press the Xbox button, or say “Xbox, go home.”
Andy: 2.Select your Profile tile (the tall tile on the left side of the Home screen).
Andy: 3.Select the friend that you would you like to party with.
Andy: 4.On that friend’s gamercard, scroll down to Join and select Party.
you: ok.
Andy: Please let me know once you're in okay?
you: yes, got into a party and i could hear them and they could hear me.
Andy: Alright! It means your audio is working now?
you: sounds like it. so, were those steps a permanent fix or is it possible i'll have to go through them again?
Andy: You're issue now was resolve and no worries, you will not experience this kind of issue again okay?
Hope this works for your nephew. If not, I'd suggest he call MS support. They were very helpful.
Last edited by LeemzHQ; 06/03/15 12:51 AM.