I might have a fix for you all. (On PC)
If you can’t join or host an Xbox Live multiplayer game, or you can’t connect to a party chat session, press the Start button , select Settings > Gaming > Xbox Networking, and look for NAT Type under Xbox Live multiplayer.
If it says Teredo is unable to qualify, it means your PC is unable to obtain a Teredo IP address.
Press Fix It
Restart your PC
It should be fixed now. It worked for me.
Just remember that it won't fix other problems like overloaded servers and overloaded internet networks (Because more people are at home nowadays.)
Have fun.