Inability to play backwards compatible games.

That's very interesting. Was that other Xbox One console running the preview update as well, or is it running the public release?

This is starting to look like a network related issue, but let's try some additional steps to help us confirm. First, let's try these steps below that in some cases helps resolve NAT issues caused by certain network hardware not being able to support multiple
Xbox consoles:

• Press and hold power button on your Xbox One console until the console fully powers down.
  
• Unplug power from the back of the console and let it sit throughout these steps. (Not super necessary, but worth doing)
  
• Power cycle your router and modem by unplugging the power from both of them.
  
• Let everything sit for 3-5 minutes.
• After the time passes, plug everything back in and power on your Xbox One console and immediately try launching a back compat title.
  
• Let us know the results! If those steps do not work, posting back with the make and model of your router and modem will be nice to know.
  

Whether you actually do own an Xbox 360 console and Xbox One console, or are primarily using an Xbox One console, those steps above are definitely

Additionally, if those steps do not work, I recommend bringing your Xbox One console to a nearby friend or family's place to try on a different network completely. I know that's definitely not an ideal step, but this will help us a bunch.

Let us know how it goes!

Hello Mister Quimby,

I tried what you listed; unfortunately, I'm still getting the same issue. For your 4th step, my xbox didn't require me or have any pop screen that gave me an option to select anything after restarting.

I also deleted the games and reinstalled them and tried the steps again, but it is still not showing my profile upon entering an Xbox 360 compatible game.

Please let me know what to try next.

Thanks.

Im sorry but take this to microsoft chat support here.

support.xbox.com/.../contact-us

Hey there, Howling Mad Doc! It definitely could be related to having another gamertag. If you still have access to that account, I would try downloading that again and seeing if you have access to those games once you make your console that gamertag's Home
console, too.

We do not suggest contacting phone support to "reset your profile". We're not aware of phone or chat support having that ability. If you need to be referred to phone or chat support for anything, one of us Official Staff agents will be sure to point you
in that direction. Right now, you're in the best place that can help you.

I wanted to clarify one thing you had mentioned. While Halo: Reach is backward compatible, the MCC version of Reach is actually through the Halo 3 Campaign in MCC, not the same version that is backward compatible. You should be able to play that from within
MCC if you got the code from the Thank You Offer last year.

As for the other games, you can check if you own them on this profile by going to the
My Games page. Let us know if you see them there or not.

no this would not be the cause (unless the dlc codes (360 games) where on the other gamertag and that gamertag isn't signed in and/or isn't home gold on your xbox one).

you can play single player games on 360 when using home gold and not being signed in with same account but you cannot play multiplayer as 360 did not have home gold and xbox one is emulating the 360 system.

last resort I would try is making sure system is up to date with latest system update and if it is call xbox support via phone and see if they can reset your profile through xbox live as a last resort (you still get your gamerescore and all just a fresh
clear from cache on xbox live side)

hope everything works out for you.