Modern warfare won’t start saying person who owns game must sign in but I have the game and...

Yea if the download isn't under your profile you'll run in to that issue...if that's not the case you may actually have to contact support.

Hello Cnln,

Thank you for posting on the Xbox forums. We understand that your are unable to launch Call of Duty: Modern Warfare due to the console not detecting the license for the game on your account. We recommend checking

the order history for the transaction for the game. Also, we suggest making sure that license for the game appears on your
game list on the Xbox website. Is there another account that is sharing it's games, content and subscriptions by using the

home console feature? Be sure to let us know the results Cnln!

I had to uninstall and reinstall my game for it to work.

Do you game share with somebody

Are there any other profiles on your Xbox console. Maybe the game accidently got purchased on one of those accounts. If not maybe the person you gameshare with kicked you out. Check your order history as well and you may be able to resolve this at https://support.microsoft.com/en-us/contactus/