On September 20 I received the email that I had been selected for the Halo Infinite Multiplayer Technical Preview. It said that I would receive another email in the following days about how to install but I never received said email. Today, September 23, I received the tech preview through Xbox Insider, and I was able to download the Tech Preview. The game loads to the start screen and tells me to “Press A to Play” but when I do so, I get the message “ATTENTION Your account is not authorized to play Halo Infinite.” Anyone else having this problem? I really got my hopes up here.
I’ve got the same issue as far as being invited on the 20th, but no actual invite sent to my account.
Also did not receive my invite tot he Technical preview. Looking for my code as well. Got a lot of friends playing tomorrow. Any help would be greatly appreciated.
I got an invite no key or anything can’t even pre download it 
I got an invite, I got the follow up emails/messages (at the top of this halowaypoint page, you might have a new notification… check it) on how and where to download.
Downloaded it and signed in once and all was fine.
Closed game and went back into game to add my controller and now all it says after logging in:
“ATTENTION Your account is not authorized to play Halo Infinite.”
Keep trying… i eventually got back in after having to input a lot of codes sent to email while trying to login with Microsoft account ID + code.
Eventually it stopped wanting the code and changed back to my actual password to login and then i got in.
I assume it is either stuck in a loop cycle somehow or has heavy site traffic while everyone is trying to get in… shrugs. (Someone else will know)
Fellas. Go into Xbox Insider on console. It is under preview. Then download and play. See online.