Xbox PC app doesn't easily let me install delisted DLC that I already own

Hello Rollingtheoc, this is Manuela. I'm an Independent Advisor and community user like you, ready to assist with this.
Not a Microsoft employee.

Actually, you can follow the next steps to install your owned games:

Open the Xbox app on your PC > click on the "My Library" tab > you should be able to see Forza Motorsport 7 and all your purchased games listed there.

If my friend wanted to use my Game Pass on PC, they could easily employ the same workaround I've already described, the current implementation doesn't prevent sharing.

They should allow you to sign into the Xbox app with whatever account you want, and then limit the number of devices Game Pass can be logged into simultaneously.

Instead I'm stuck with their current implementation that prevents me from easily using it on my own PC.

The game and DLC was delisted a while back so it's no longer possible to get it from the Xbox store. If you own it on your account, you should be able to install it by highlighting the game on the dashboard or in games and apps, press the menu button, and go to manage game.

Please try these steps:

1) Install the DLC directly from the Microsoft Store.

Open the Microsoft Store app.

Make sure you're signed in with the same account used to purchase the DLC.

Search for the specific Dead by Daylight DLC.

On the DLC’s page, it should say “Owned”, if so, click Install or Get.

2) Try a force license refresh.

Sign out of both the Xbox app and Microsoft Store.

Reboot your PC.

Sign back in to both apps with the same account.

Let me know if these worked.

as i said in my post, warner bros had it delisted from all platforms. this is down to licences expiring, many games get delisted every year, if you already owned it then you get to keep it but once delisted then the game and dlc are no longer available for purchase.