If you have received an invitation but Microsoft Flight Simulator doesn't appear in the Xbox Insider Hub, please do the following:
1. Make sure that you're signed in with the Microsoft email address/account linked to your invitation and not a different gamertag. You must be logged in both the Microsoft Store and the Xbox Insider Hub with the same email address/account.
2. Install the Xbox Companion app (Beta) app for Windows 10 PC here: https://www.xbox.com/en-US/xbox-app
3. Make sure Windows has the latest update: Select Start , then select Settings > Update & Security > Windows Update > Check for Updates.