Halo 4 Boots Me Back to Menu (PC/Steam)

Every time I try to load up any level in Halo 4, it counts down and before the level loading screen pops up, it takes me back to the menu.
I’ve tried verifying the integrity of the files, I’ve tried uninstalling the Halo 4 portion of the game and reinstalling, and I’ve even tried doing a complete uninstall and reinstall of the entire game.

Nothing I’ve done seems to work.

As this appears to be an issue with your game, we recommend heading over to https://aka.ms/HaloSupport for further assistance. Please review the latest known issues and submit a ticket if your issue is not listed.

Thanks!

I fixed the problem. Make sure your Multiplayer files are installed.