With Halo Infinite finally releasing after nearly a year-long delay, everyone is eager to play it. Unfortunately, some players are running into problems when trying to do just that. If you are wondering why you cannot play the Halo Infinite campaign right now, then there are a couple of reasons.
First up, the preload was not really a preload. Yes, you downloaded some of the game, but there are still parts you need to download now that the game has gone live. This even applies to people who bought the game on disk, there was no complete game on that disk and you still need to download some information.
Secondly, just like you, the world is excited about the Halo Infinite campaign. It is also free on Game Pass, so the sheer number of people trying to download it is huge. This means the servers are getting smashed by huge volumes of people all trying to download the same information from the same place.
Unfortunately, there is nothing you can do and you will just need to be patient and wait for the issue to resolve itself. It is sadly just part of modern gaming that even single-player experiences will always seem to have some form of online requirement to be playable.
You may also need to actually install the campaign, which you can do by going into specific menus and instructing the game to do so.