Soooooo I updated the 40 plus GB update to play the new stuff and to play mainly reach. Well when I updated it and went to the games I had installed, Halo reach campain and multiplayer was there. But for some reason, when I went to the custom game section and clicked on Halo Reach it said I dont have that content downloaded? So I uninstalled reach and download the campain and multiplayer again. Still nothing worked at all, same text and same issue.
Same thing happened to me, I just ended up uninstalling MCC and I’m in the process of reinstalling it right now
That is weird indeed, if it were campaign or firefight you need to get the key from the Microsoft store. Maybe you could try that?
That’s super weird, doesn’t really make sense, seems like as if both the last update and the new update are interfering as if the game is truly installed but update isn’t reading it. That’s really odd
I reinstalled the whole game and it now works fine for me
I was hoping I didn’t have to uninstall 
thank you