"Account not authorized to play Halo Infinite"

Hey everyone.
I have been invited to play the Halo Infinite flight of this weekend and the next, but after downloading the Halo: Infinite - Insider from the Xbox Insider Hub (on the original Xbox One), i can’t proceed after pressing the “A” button on the main menu.
When i do it, it shows that my account is not authorized to play Halo Infinite.
I have restarted my console several times already, to no effect. I have erased the save data, but it didn’t work. I have uninstalled the game and installed it again, but nothing happened. And yes, i am using my gamertag that is associated with my invite to the flight.
Can someone report on this? Do you have the same issue? If you do, have you managed to play the game already? If yes, what did you do to make it work?
And if you have the same issue and still cannot play, share with us below, so we can discuss more about it.