Can't connect to ONE friend only, help please!?!

Real quick i'll be honest the subject is a little off, its two friends and i'm pretty sure it's the NAT I just want to know if it is NAT and how to fix it. So, my problem is, I can connect with ALL my friends on Xbox Live except two, its as if I loose connection
when I try to communicate with them. I can message them, but I can't party, or join games. They can connect with all their friends but me! I have tested my connection and there is nothing wrong but they have not tested theres, help anyone?

:)

 

Headset

I'm trying to connect xbox one official headset. I can hear my friends but they can't hear me. I have tried to set it with the controller but it says no update needed. Please help

 

Can't join only one friend's party chats

Me and one of my friends cannot connect to each other via party chats or game invites. This only happens with this one friend. I can't seem to figure out why this is. We can both connect to our other friends just fine. We are both on wireless connections
and I have a open NAT type and he has a Open NAT type. Help me?

 

Maybe they blocked you.....

 

Probably best if they test theirs first to see if it's their end. It can be a funny thing NAT. I once had a moderate nat type and although I could connect to my friends they sometimes couldn't connect to me.

 

Check out Setup a port forward in your router to allow incoming connections for multiplayer games, VOIP, DVR, and security cameras. this site should have step by step instructions on how to open your Nat on your router for your Xbox 360 or XboxOne.