I spent a bit of time fidding with it yesterday trying to get it to work. There's quite a few instances on google of people with the same problem (but not in a Tesla). Basically it'll load, you get the spaceship, then the xbox logo, then a black screen until it quits. Some people have solved it by clearing cache etc (which I did try in the Tesla but it didn't help).
eg:
XBox Cloud - We'll be right back error :: Steam Deck General Discussions
and
Redirecting
So I think it still probably rests on Tesla to update the browser to fix this, I don't think it's at xbox's end unfortunately. Could also potentially be Telstra