I don’t know if this is a common issue among many but there is a bug that prevents you from playing matchmaking. For about a month now I haven’t been able to play any of the playlists in Halo’s matchmaking.
After hard resetting and trying every troubleshooting solution under the sun. I decided that I would just uninstall the game along with the massive over 20 gigabyte update that Is required for the game to function.
I then reinstalled it and then waited for nearly two days to install the massive bloated update.
I booted it up and now it is working again.
So to all the people out there that haven’t given up on this game and are in similar shoes. Hopefully it works and solves the problem for you.
Just thought I’d share 
Glad that worked for you (:
I tried it but it didn’t, so I’m stuck since three weeks and still no word from 343 that they are even aware this bug exists.
I have seen Bravo respond to a tweet from ‘TheCrazedSpartan’ by saying that they are looking into it.
It absolutely bugs the *$&!#! out of me that 343 have not got a list on this website of bugs that they are working on. They stopped updating the ‘bug investigation’ thread way back in January. (In the MCC support forum).
Now, ‘TheCrazedSpartan’ seems like a really nice guy and his Youtube channel is well worth a visit but, why on earth is Bravo responding to him and not informing the hordes of people who come on this site and look for answers?
And nothing in the community updates.
I think 343 are shocked that people are actually still trying to play this game and don’t quite know what to say.
They aint getting a penny of my money. I will not be buying H5 new.
Seriously, do check out Crazed’s channel. Here is another link