When I launch the newly installed Halo Reach through Steam, I get the following error message:
“Something went wrong. There is a problem with your Microsoft account. To fix this, sign in to account.live.com from a browser.”
After signing in to the link provided nothing fixes the issue and I still can’t access the Main Menu of the game to start Campaign or play Multiplayer. Any help regarding this would be amazing. I’ve also submitted a ticket through Microsoft after two unsuccessful attempts to get customer service over the phone.
I’m not saying this is your exact issue but this could be the problem,
Uninstalling the Steam version of the game with the Microsoft Store version installed will remove the Easy Anti-Cheat client and make the Microsoft Store game be unplayable. To resolve this please uninstall and re-install the Microsoft Store version.
Also, I would try to uninstall Halo Reach sign out of steam, restart your PC and then once it is restarted, sign back in and redownload it,