Hey guys I had a recent problem with the halo 4 map pass and here is the solution in case it happened to you too. Well the problem was that when I went to purchase the map pass it said my privacy settings were not letting me but it. On an Xbox, it's easily solved (dashboard/settings/privacy) but on an Xbox 360 here is the solution.
Go to the www.xboxlive.com In the top right hand corner, press sign in. Then in the same corner, press my account. Go down and on the far right, second from the bottom it says "privacy and online settings" Go into it and change the "purchasing" tab to allowed.
Hope this helps!