I just started having this problem a few hours ago, I haven't joined any parties for around half or three quarters of a month but it worked fine last time I tried.
My friend and I wanted to play Halo 4 today but it kept saying "cannot connect to party, there may be a network connection issue, your NAT is open and suitable for joining" or something along those lines.
Is it something inside my Xbox or is it a glitch because I just downloaded the new update from Halo 4 a while earlier today, and now it's not working. My friend also said that her Xbox started acting weird a couple of days ago, around when she downloaded the update, but I don't think that's the case. While I'm fairly sure it was a game update, I might have missed a console update pop up but I just clicked A without looking, so was their a console update? If there was, is anyone else having the same problems as me?
I also tried to join other people's parties and I tried to send messages but I can't join their party either. I'm not sure if my messages are being sent correctly either because my friend said she got a blank message from me but I did type "asdfgv" or something, and no one else replied yet.
If it depends on the location then I live in the Lower Mainland area of BC, Canada.
If this is a NAT problem can someone please simplify how to fix it in case unplugging everything doesn't work?