I have posted on this with no response from Bungie. Question -- are you getting one of the animal error codes or just the message "You have left your fire team and been returned to orbit"? If the former then check out the Bungie network set up guide and the explanation for that particular error. If the latter then clear cache by unplugging your XBOX ONE, then reset your router, and after it is running again, power up your XBOX ONE. That may solve your problem. However, if you have a new Slim and are using an elite controller with it, then you have the same problem I did for which I got no response from Bungie. With that set up I could not make the problem go away. When I used the Slim supplied controller the problem disappeared. So the choice is either don't use the elite controller or return the Slim. I returned the Slim and am using my older XBOX ONE Elite with no issues. Btw, XBOX Support says that the elite controller and Slim are compatible.