Try this, it worked for me:
Just go to Device Manager -> View -> Show hidden devices
Uninstall Teredo Tunneling Pseudo-Interface (don’t worry, it will come back again)
Open a command prompt (Run as administrator)
Then type the following commands:
netsh int teredo set state disable
netsh interface teredo set state type=client
Confirm that IPv6 is working by typing:
netsh int teredo show state
If the “State” says “qualified” try to open Killer Instinct again and go multiplayer.
I hope it helps.