Xbox Series X FH5-HW purchase

I own a series x, I have the full game and seasons pass on this unit.
My son is playing FH5 on this unit, he wanted to play FH5 Hot Wheels, ehen he goes to the map it is asking to purchase the expansion even tho it is on the same unit he is currently trying to play on.
I have been playing it from day one, why it is asking for a purchase is crazy.

He does not get access to add-ins that you purchased for your account. He only gets access to your Xbox Game Pass and base games. If he wants to play the Hot Wheels Expansion, then you need to buy it for his account.

I actually already had this xbox webpage open with this information on sharing.

https://support.xbox.com/en-US/help/family-online-safety/shared-consoles/concurrent-signin

He should be able to play it. You just have to make sure you and maybe him too have the Series X set as your home console.

Settings>general>personalization>my home Xbox.