Just a post that I hope may help some people struggling like to to access the Halo Channel and the Halo 5 MP beta. I haven’t seen this posted anywhere, but apologies if it is a duplicate post.
I discovered that it was my DNS settings. I use Norton DNS to stop the kids getting to places they shouldn’t, never had a problem before, but for some reason Norton have halowaypoint.com marked as violence so all requests were being routed to a ‘You can’t access this’ holding page but I didn’t know that because I was only getting errors that the channel was unavailable or the servers were unavailable.
Switched the DNS settings on the xbox one to normal DNS and all is working great.
Hope it helps somebody.
[Edit for typos]