My Xbox Series X won't launch the game after installing how do I fix it?

The backwards compatibility team is working on the Series X so there won't be anymore games from the 360/original Xbox made back compatible until after the Series X launch.

That said, I would love to see Gotham City Impostors made playable on the Series X. That game was so much fun!

Annnddd it's back - but now flipped.

After the fix (thank you @Smwutches), everything was working well on both my Xboxes. We've been playing them both daily since December 23rd without any issues.

Today both my kids and myself played my Series X repeatedly without any issues - bouncing between both Game Pass and purchased games.

After my kids finished playing, I took over and was playing my Series X, but had to soft restart it due to a game (The Division) crashing in the load screen. After playing it for a few minutes, I closed it out and went to play a Games Pass game, only to get the dreaded "The person who bought this needs to sign in or go to the Microsoft Store". I even tried games I'd seen my kids play a few hours ago with no issue - now they won't launch and instead give this error. I also tried to simply do some Cloud Gaming - although I could launch the Game Pass game, it errors out when I try to launch via Cloud.

I confirmed that the Series X is NOT checked as the Home Xbox, and the Xbox One IS checked as the Home Xbox. No difference from where it was when we last solved this issue.

Any clue what is happening here, how to fix it, and avoid it from happening again? This is not only frustrating, it's a bit confusing that it seems to be randomly happening.

With the Xbox One X you'll be safe to wait well after launch to buy the new Series X.

They've already said that launch games like Halo Infinite will also be launched for Xbox One consoles.

I've had my Xbox One X for over a year. I plan to buy the Xbox Series X for my main television and then move my Xbox One X to my living room television as my secondary console.

Check your network connection. You may need to restart your network hardware to reestablish a connection to your ISP.

Would a network issue stop games from launching?

OP: Which platform are you on? Xbox (XB1 or Series X/S) or PC? Is it all games or just particular ones? When you say loading, do you mean the game won't launch or they won't install?

I will buy a Series X, but not on launch. Also not sure if we will get all the services at the local launch in my region or when it will be launched locally. With the Xbox One we had to wait a whole year after the international launch. One X we where lucky
to get it a month after.

I don't think new games will be playable on the older consoles, just Xbox One family of consoles and the Series X.

Will need to wait for more information regarding this.