Da Davesta

I cannot connect to Halo 5 multiplayer servers. Every time I start the game it comes up with the error message " ATTENTION Error authorising user with Halo 5 Guardians server. You will be unable to access online modes." I have reported the problem to Xbox live support who have checked my account and found no issues so they referred me to this site. I don't have any problems playing multiplayer on other games. My ISP is Sky. I agree with the others - fix or money back please!!!