So my sister and I have been playing Halo and as soon as we press one of the games to start searching for players, it will say “Leaving” like one of us has backed out, but neither of us have. It’s done it several times and even when they’ve found players and we have voted on a map it will say “Leaving” and then we have to go through the entire process again. The thing that has pissed me off is now since it has made us leave several times, we’re banned from matchmaking? any clue as to why and what to do?

Haven’t had that problem but I would suspect a NAT type on your console. When you test your xbox live connection what NAT type does the console report? Does this happen when you try matchmaking solo? As far as I know MCC matchmaking is P2P based, so there it makes a difference to have open NAT versus moderate or closed.

Try doing a hard reset on your console, then attempt it.