I have been dealing with the same issue for over a week now. Game has been updated twice in that time and I still cannot get into the game.
Please have a quick look at your NAT type and ensure it is set to "open".
Additionally, can you tell us if you're a part of the XBOX Insider program? (if yes - try opting out and see if that allows you in).
If not, and your NAT type is indeed set to open, can you create a ticket over on support.deadbydaylight.com ? We're trying to gather some data on this at the moment.