Me and my friend playing on Steam can’t play Halo ce, we tried to play the first 2 missions but it kept giving us a blackscreen and then it would show the loading screen for the host while the 2nd player gets kicked back to the main menu, the host would also get kicked to the main menu after the loading screen.
Sounds like this issue listed in the known issues section on the Support site: ‘In Halo: Combat Evolved Anniversary co-op campaign, both players are sometimes returned to menus with a disconnect error when loading into the campaign if players have significantly different load times.’ - no mention of a workaround listed.