I have never been able to access multiplayer games before, as I have never had xbox gold. That, however, wasn’t the only thing stopping me, as every game has always reminded me that multiplayer contect is restricted for my account. I do have a kids account, and I have worked with my parents to try to figure something out so that I can play multiplayer. Now, with halo Infinite’s free to play multiplayer and the fact that similar reasons are stopping me from playing the flight, I decided to take my issue to the general public and see what I could get out of it. I know this is only partially related to halo, let alone halo mcc, but I might as well give it a shot.
If you are under the age of 18 then you won’t be able to take part in the Halo Insider program for flighting I’m afraid, it’s a legal requirement related to data protection/privacy and storing of data.
For regular multiplayer, if you’re having issues accessing online play with your account then it’s likely related to your Xbox privacy settings. Xbox Support should be able to help you adjust the correct settings either on your console or via the web: https://support.xbox.com/en-US/help/family-online-safety/browse