Halo: CE Anniversy Co-Op Issue.[PLEASE HELP]

I’m trying to play co-op with Halo CE with my brother and it’s not working. It keeps kicking us out or the game freezes up on his end. It says connection lost and we’ve tried so many solutions that don’t work, solutions like turning on relay, fixing the net settings, and even both entering the same mission in single-player and exiting, waiting, and then joining in co op again, none of those work. It’s frustrating because Halo: Reach co-op works perfectly fine but Halo CE co-op just does not. PLEASE get this FIXED, it’s incredibly FRUSTRATING for me and I would like to play co-op without having any issues like this arise.

P.S: Off-topic, but am I the only one here that gets a texture glitch when I reach the library mission in Halo CE where everything looks flat and ugly? And Cortana reverts to the classic graphics look?