Shadow of the Tomb Raider DLC Unavailable

Before I explain this issue, can I just say that not being able to contact XB Support by phone or chat for this type of problem is just wrong. It's bad enough enough that I've wasted countless hours online researching the problem and communicating with developer
Square Enix, who finally determined that this is a MS / XB licensing problem. And bad enough I can't play any of the Add-On content that came with the expensive Definitive Edition. Not being able to speak or chat directly to an agent is just adding insult
to injury. In any even, here's what's happening and what I've tried. If anyone can help (or maybe even explain how I might actually communicate with XB directly, I would be eternally grateful.

I am unable to access any of the DLC that came with my digital copy of the Definitive Edition of The Shadow of the Tomb Raider I purchased from the XB Store on my Xbox One-X. Much of the add-on missions, challenge tombs, and gear wasn't available until sometime
after the initial release. However, when I recently came back to the game to play all the DLC (and the Definitive Edition is supposed to include ALL DLC), I couldn't access.

I've been in contact with the Square Enix developer, who confirmed that my multiple play-through of the main campaign reached all the progress point requirements. After they walked me through several troubleshooting procedures, they determined that for some
reason my XB1-X isn't recognizing the DLC license within the game. And as a result, they said I needed to contact XB for support. (Which of course, XB won't even let me do.)

Problem: None of the DLC Challenge Tombs and missions appear at ANY point in the game. None of the Mission Giver characters appear where and when they're supposed to. When I click on the DLC "Additional Challenge Tombs" in the game's Main Menu, all of the
tombs have shopping cart icons by them. And if I click on those, it takes me to the XB Store, which in turn tells me they're already installed.

Troubleshooting Attempted: Based on Square Enix's instructions, as well as fixes attempted by others who reported the same problem on various forums, I have tried the following (some several times).

Performed a hard reboot of my console (removing the power cord). Made sure my XB1-X is fully updated.

Uninstalled and reinstalled the base game and all the DLC files (several times); both all at once, and then again, one at a time (and given there are 32 files, this was highly time consuming).

And each time I did the above, I also started a new game to verify I was progressing the story to points where the DLC should have become available.

I have been struggling with this for far too long now. I've spent countless hours just trying to access the DLC I paid for and have never been able to play. I really don't mean to be overly demanding and I don't think it's unreasonable to expect to
be able to play what I paid for. Especially given the amount of money I paid Microsoft / XB for the Definitive Edition of this game. Truly, I just want to play what I paid for. Please help!

:)