Trying to find games in any playlist… Always get “failed to connect”. I don’t see any other players either. It will say “Players Found” but no one is ever listed in the lobby. Anybody else?
I’m havering this same issue. So your not the only one mate.
For now, make sure you have reset the console by holding power button till it turns off (about 10 secs).
If you’ve done that, we’ll work from there 
The Master Chief Collection is everything I could ever want out of Halo. Who needs working matchmaking when you have a campaign mode that will only be played once? Gamers are so spoiled these days. Back in my day we didn’t even have the internet.