While this could be a temporary issue, please be sure you're both synced with your Microsoft (Xbox Live) Accounts in the settings menus, and try re-sending the game invitation after. I hope this helps! ^SA
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
While this could be a temporary issue, please be sure you're both synced with your Microsoft (Xbox Live) Accounts in the settings menus, and try re-sending the game invitation after. I hope this helps! ^SA