Hi there! My name is David. It’s a pleasure to help you today.
Thanks for sharing your question, I’m going to suggest a few things that might help you solve the issue:
Confirm that you are signed in with the same account you used to purchase the add-ons:
Open the Microsoft Store > In the upper right corner click on the profile icon and check if you are signed in with the correct account.
Inside the Microsoft Store go to “Library” > Games > Look for the purchased Forza Horizon 5 add-ons.
Open the Xbox app > In the upper left corner, check if you are signed in with the correct account.
Inside the Xbox app > Go to “My Library” > look for “Forza Horizon 5” > right-click on it > click “Manage” > go to the “Add-ons” tab > confirm that all the game add-ons are selected, otherwise check them all and click “Apply Changes” so they can be downloaded and installed.
Let me know if the shared information has been helpful. Regards.