How do I get vault edition working without disc since I started with disc version & only...

Hi, I hope you're doing great out there. I am an Independent advisor and I am here to help you in regard to your concern.

Just a friendly reminder though that for physical disc versions, the license is on the disc itself which means that to play the game we need to have the disc insert.

To confirm, do you have the standard version of Call of Duty Modern Warfare II for Xbox Console?

Also, is your son using a different Xbox Console than yours?

You have also mentioned the PS5 version of the game, can you please share with me details in that way I can get into the issue further?

That explains it then. DLC discs are usually only shipped as a package with the full game. These discs usually only work with the version of the game it came with and no other version. If the disc you purchased was part of a game of the year edition then
you'll need to get a copy of that disc.

Yes, you can buy the Vault Edition upgrade if you have the disc version of the game.

why is this happening can someone please help me

To confirm, was it the vault edition ($100 USD if in the US) or the vault edition upgrade ($30 USD if in the US).

If it was simply the upgrade, then do you also already own the digital crossplay version of MW3 on your own account? If you dont (either someone is gamesharing it to you or you have it physically on disc) then the vault edition upgrade wont work for you.

Yes, you can buy the Vault Edition upgrade if you have the disc version of the game.

No you cannot actually per https://www.xbox.com/en-US/games/store/call-of-duty-modern-warfare-iii-vault-edition-upgrade/9PK2J9GDNWW3 it says:

"Call of Duty®: Modern Warfare® III digital Cross-Gen Bundle required to redeem upgrade content. Sold separately."

Unless the description is just flat out wrong then the disc version won't work with the upgrade. They must have the digital version.