Halo Infinite's campaign has been highly anticipated, and with launch day finally arriving, many players will be wanting to jump in immediately. Unfortunately, with everyone downloading at the same time, the servers will be slammed as everyone tries to download the Halo Infinite campaign. As a result, some players may be wondering why they cannot play the Halo Infinite campaign.
Update: Dec. 8 2:05 EST
We are currently having trouble launching the game on PC Game Pass. We are currently investigating ways to fix this. Some users are reporting success with these methods. We were able to purchase the Halo Infinite campaign on Steam and launch it first try.
The servers are likely at capacity, slowing down all players' downloads. Unfortunately, the only real solution is to be patient and wait for your download to complete. Minimize other usages of your internet and if you can, move your PC or Xbox closer to your router and plug in an Ethernet cord.
Related: How to unlock multiplayer armor in the campaign for Halo Infinite?
As players cannot pre-load the Halo Infinite campaign and even physical copies of Halo Infinite require a download, everyone will be in the same boat. This many players trying to download the game at the same time will put a major throttle on the servers which will keep some players from playing Halo Infinite's campaign.
With the launch of a massive game like Halo Infinite, these things are likely to occur. Keep your download going and try to minimize other usages of your internet to make this process as quick as possible.
For more information on Halo, check out How to get the Abbey Lime skin in Halo Infinite Multiplayer? and Every Hidden Alternate/Variant Weapon in Halo Infinite on Pro Game Guides.