A sign in change has occured

Let's try to power cycle your console. Please hold down the power button on the front of the console for approximately 15 seconds until the power light shuts off. Wait about 60 seconds, then power it back on. Be sure you see the green "XBOX ONE" animation
loading screen when you power it back up. Reset you're router too and be sure you are logged in the account you buy the game.

it sounds as if someone is signing in with your account on another Xbox

go to the following link and it will guide you through the process of securing your account.

https://support.xbox.com/en-US/my-account/security/compromised-account-solution

read the instructions carefully as they tell you how to do this without alerting the person using your account

Hey there Teresa!

Sorry to hear that you're dealing with those Assassin's Creed problems. I just wanted to add that if the aforementioned power cycling didn't help, then I would go ahead and try the steps outlined on our support page entitled "My
Xbox One game won't start or freezes during gameplay". It helps with a variety of issues, including a majority of game crashes.

Give that guide a look through, those steps a shot, and let us know how that helps in resolution of your issue.

Thanks!

It occasionally does that with ME2 for me and it has done it once with the ME3 demo. I honestly do not know why it keeps doing it.

Heya!

We are not quite sure what error you are referring to. Could you post a photo of the error so we can get a better idea of what is going on?

If you are on the Xbox One console be sure to follow the
random sign out guide.

Post back and let us know!