Halo Reach Multi Threat chest

Hi there ISneaky,

Thanks for reaching out here in Xbox Forums. I understand there is an issue with in-game downloadable content. I recommend to trythe following article:
How to restart or power cycle your Xbox One console (Disconnect and reconnect your console's
power cable)

If the issue persists, I recommend to contact Halo Support for more in-game assistance.

Try this and let us know the results.

I found the following information to what you ask

1. The Bungie Eternal blue flames are no longer available since they were only available for a limited time before the franchise was handed over to 343.

2. The Legendary red flames were only available with brand new copies of the Legendary edition of Halo Reach. The only way to get these is to buy a new copy (which probably doesn't exist anymore) .

3. The Elite Officer armour was only available with brand new copies of the Limited/Legendary editions of Halo Reach.

4. The 3rd variant of the Recon helmet was a pre-order exclusive.

5. The U/A Multi-threat chest piece was another pre-order exclusive.

6. The Security chest and CQB/Military Police helmets are available to unlock through the Halo Waypoint app on Xbox 360, but you will need to earn specific achievements across Halo 3, ODST and Reach, as
well as having a specific career milestone for earning achievements across all Halo games in order to unlock them.

Campaign;

1. Halo CE
2. Halo Reach
3. Halo 3
4. Halo ODST
   
5. Halo 2

Multi-Player;

1. Halo Reach
2. Halo 3
3. Halo 2
4. Halo CE
   

Yeah, I'd prefer to do it solo, if I buy this game it won't be for multiplayer, Halo multi's been terrible since Reach.

I have had the Halo Master Chief collection since December and its great as it has Halo 1-4 and their multi-player but sadly Reach is not in it (yet*) and ODST is getting implemented for a price sometime this month (May) and if that does well we might get
Reach* at some-point (Reach was awesome!).