Xbox One multiplayer online gaming

[#1]

Hi everyone, I’m really hoping someone can help! I have done lots of searching online and called plusnet with no solution.  I have been with plusnet for year and now i am having problems with my XBox one. I cannot use multiplayer function on certain games. I’ve tried the following:

Port forwarding

Turning off x box one and router and restarting

UPnP on

DMZ enable to the XBox one

Nat setting open

It's got to be something to do with plusnet as when i use my phone as a hotspot it works. says something about Teredo blocking multipalyer. i've read that having a static line or something helps but not sure what that means!

Does anyone know of any solutions please? It's driving me nuts. 

Thanks for reading.

[#2]

My stepson has not been able to play on his xbox one for four days, frustrated teenager causing hell at the moment.

When it does work he says it lags a lot? I'm trying to keep the peace but sorry I can't help, hoping to get mine sorted to.